
// Make newform 2898.2.a.bh in Magma, downloaded from the LMFDB on 24 April 2024.
// To make the character of type GrpDrchElt, type "MakeCharacter_2898_a();"
// To make the coeffs of the qexp of the newform in the Hecke field type "qexpCoeffs();"
// To make the newform (type ModFrm), type "MakeNewformModFrm_2898_2_a_bh();".
// This may take a long time!  To see verbose output, uncomment the SetVerbose lines below.
// The precision argument determines an initial guess on how many Fourier coefficients to use.
// This guess is increased enough to uniquely determine the newform.
// To make the Hecke irreducible modular symbols subspace (type ModSym)
// containing the newform, type "MakeNewformModSym_2898_2_a_bh();".
// This may take a long time!  To see verbose output, uncomment the SetVerbose line below.
// The default sign is -1.  You can change this with the optional parameter "sign".
function ConvertToHeckeField(input: pass_field := false, Kf := [])
    if not pass_field then
        poly := [24, -8, -18, 0, 1];
        Kf := NumberField(Polynomial([elt : elt in poly]));
        AssignNames(~Kf, ["nu"]);
    end if;
    Rf_num := [[1, 0, 0, 0], [0, 1, 0, 0], [12, -14, -2, 1], [-24, -18, 2, 1]];
    Rf_basisdens := [1, 1, 4, 4];
    Rf_basisnums := ChangeUniverse([[z : z in elt] : elt in Rf_num], Kf);
    Rfbasis := [Rf_basisnums[i]/Rf_basisdens[i] : i in [1..Degree(Kf)]];
    inp_vec := Vector(Rfbasis)*ChangeRing(Transpose(Matrix([[elt : elt in row] : row in input])),Kf);
    return Eltseq(inp_vec);
end function;


// To make the character of type GrpDrchElt, type "MakeCharacter_2898_a();"
function MakeCharacter_2898_a()
    N := 2898;
    order := 1;
    char_gens := [1289, 829, 1891];
    v := [1, 1, 1];
    // chi(gens[i]) = zeta^v[i]
    assert UnitGenerators(DirichletGroup(N)) eq char_gens;
    F := CyclotomicField(order);
    chi := DirichletCharacterFromValuesOnUnitGenerators(DirichletGroup(N,F),[F|F.1^e:e in v]);
    return MinimalBaseRingCharacter(chi);
end function;

function MakeCharacter_2898_a_Hecke(Kf)
    return MakeCharacter_2898_a();
end function;


function ExtendMultiplicatively(weight, aps, character)
    prec := NextPrime(NthPrime(#aps)) - 1; // we will able to figure out a_0 ... a_prec
    primes := PrimesUpTo(prec);
    prime_powers := primes;
    assert #primes eq #aps;
    log_prec := Floor(Log(prec)/Log(2)); // prec < 2^(log_prec+1)
    F := Universe(aps);
    FXY<X, Y> := PolynomialRing(F, 2);
    // 1/(1 - a_p T + p^(weight - 1) * char(p) T^2) = 1 + a_p T + a_{p^2} T^2 + ...
    R<T> := PowerSeriesRing(FXY : Precision := log_prec + 1);
    recursion := Coefficients(1/(1 - X*T + Y*T^2));
    coeffs := [F!0: i in [1..(prec+1)]];
    coeffs[1] := 1; //a_1
    for i := 1 to #primes do
        p := primes[i];
        coeffs[p] := aps[i];
        b := p^(weight - 1) * F!character(p);
        r := 2;
        p_power := p * p;
        //deals with powers of p
        while p_power le prec do
            Append(~prime_powers, p_power);
            coeffs[p_power] := Evaluate(recursion[r + 1], [aps[i], b]);
            p_power *:= p;
            r +:= 1;
        end while;    
    end for;
    Sort(~prime_powers);
    for pp in prime_powers do
        for k := 1 to Floor(prec/pp) do
            if GCD(k, pp) eq 1 then
                coeffs[pp*k] := coeffs[pp]*coeffs[k];
            end if;
        end for;
    end for;
    return coeffs;
end function;


function qexpCoeffs()
    // To make the coeffs of the qexp of the newform in the Hecke field type "qexpCoeffs();"
    weight := 2;
    raw_aps := [[-1, 0, 0, 0], [0, 0, 0, 0], [0, 1, 0, 0], [1, 0, 0, 0], [-2, 1, 0, 0], [0, 0, 1, 0], [0, 0, 1, 0], [0, 1, 1, 0], [-1, 0, 0, 0], [-2, 0, 0, 0], [1, -1, 0, -1], [1, 0, -1, -1], [2, 0, 0, 0], [2, 1, -2, 0], [3, 1, 0, 1], [-3, 0, -1, -1], [4, -2, 0, 0], [0, 3, 0, 0], [6, 3, 2, 0], [1, -1, 1, 1], [3, 1, 1, 1], [7, 1, 1, 1], [-2, -1, 1, -2], [-2, 0, -1, -2], [-2, -2, -1, -2], [-4, -2, 3, 0], [-4, 2, 2, 0], [-2, 1, 0, 0], [2, -1, 0, -2], [4, -2, 0, 2], [4, 0, 2, 0], [0, -2, 0, 0], [-2, -2, 0, 0], [4, -2, -2, 0], [0, 1, -2, 0], [7, -3, -1, -1], [6, -1, 0, 2], [-3, 1, -1, -1], [9, 3, 2, -1], [2, 2, -1, 2], [0, 2, 4, 0], [6, -1, 2, 2], [-5, -1, 1, 1], [11, -1, 1, -1], [0, -2, -4, -2], [4, 4, -2, 0], [-3, 3, -1, -1], [-7, -1, 4, -1], [10, -1, 1, 2], [-8, -3, 0, 0], [5, 3, 1, -1], [6, -2, 0, -2], [-6, 2, -1, -2], [10, -1, 3, -2], [-4, 2, 0, -2], [6, -2, -2, -2], [-8, 0, 1, 0], [-18, 2, 1, 0], [12, 0, -2, 2], [-2, -4, 4, 0], [8, 3, -1, 0], [14, 1, -2, 2], [4, -4, -2, 0], [8, 0, -5, -2], [-4, 4, -1, 0], [-18, 0, 2, 0], [4, 0, 0, 0], [10, 0, -2, 0], [9, -3, -1, -1], [2, 4, -1, 2], [-11, 3, 1, -1], [9, 1, -1, 3], [6, -2, 0, 2], [1, -2, 3, -1], [-8, 5, 2, 2], [14, -2, -2, -2], [-5, -2, 5, -3], [-24, 0, -1, 0], [-12, 4, -2, -2], [0, -2, 2, -2], [22, 3, 3, 2], [-4, -1, 6, 0], [6, 4, -2, 2], [0, -4, -1, 0], [-22, -2, -1, 0], [1, -7, -1, -1], [0, 2, 2, -2], [8, 0, 2, -2], [6, -2, 5, -2], [-10, 2, -2, 2], [-18, 5, 1, 2], [-12, 0, -2, 0], [10, 6, 2, -2], [1, -3, -5, -1], [-7, 1, 3, -1], [22, -4, 2, -2], [-6, -6, 1, 2], [-2, -6, 3, 2], [-4, -3, -1, 0], [-12, 0, -2, 2], [-2, 2, -6, 2], [6, -3, -8, -2], [6, -3, 5, 2], [-22, -6, -4, 0], [10, -3, 2, 0], [1, 3, 7, 3], [-2, -4, 4, 2], [-12, -10, 0, 2], [12, -4, 0, -4], [-21, 1, 1, 1], [-5, -3, 2, 1], [0, 3, -6, 0], [-12, 6, 2, 2], [4, 5, 3, 0], [-17, 7, -3, 1], [4, 8, -2, 2], [-20, -3, 3, 0], [0, 0, 3, -2], [-2, 6, 4, 4], [10, 3, -6, 4], [10, 3, -6, -2], [-8, -8, -4, 0], [-18, 1, 2, 2], [-1, -3, 1, 1], [-12, -2, 6, 0], [-30, 7, 0, 2], [7, 4, -7, 1], [20, -4, 1, -2], [-4, -8, 2, 0], [6, -3, 0, 2], [-15, 5, -1, -1], [-1, 5, -3, -3], [12, -2, 0, 0], [-16, -3, 6, 0], [-13, -3, 9, 1], [-10, 10, -3, 2], [2, 5, -4, -2], [20, 7, -3, 0], [-4, -3, -2, -4], [9, 7, 1, 3], [-28, -2, 0, 0], [-24, -4, -4, 2], [7, 5, 7, 3], [6, 5, 0, 0], [-26, 4, 1, 2], [-12, -8, 0, 0], [-10, 6, -3, -2], [3, 5, 3, 1], [-2, -6, -4, 2], [12, -8, 2, 0], [16, -12, 0, -2], [-28, 2, 3, 0], [3, 5, -7, -3], [-1, -3, 8, -3], [-10, -5, -4, -4], [17, 9, -1, -1], [3, -3, -3, 5], [-6, -4, -4, -4], [10, 0, 1, 2], [-18, -7, -6, 2], [-3, -7, -1, -5], [-10, -6, 2, -4], [7, -11, -3, -1], [-10, -1, -7, -2], [-22, -6, -4, 0], [-28, -6, 0, 0], [-1, -7, -1, -1], [34, 0, -1, -2], [-2, -6, 4, -4], [12, 6, 3, 4], [-18, 9, -4, 0], [4, -2, 7, -4], [-5, 1, 1, 1], [0, 2, 4, -2], [14, -2, 7, -4], [16, -10, 3, 0], [-22, 0, -2, 2], [-10, -2, -4, -4], [-8, -6, 4, 4], [12, 3, -10, 4], [13, -13, 1, -3], [-6, 3, -7, 2], [14, 6, -2, 4], [-15, -1, 1, 3], [24, 6, 4, 4], [-12, 9, 2, 4], [14, 0, 4, 4], [20, -11, 1, -4], [20, 4, 0, 0], [-3, 3, 4, -1], [-1, 9, 7, 5], [13, 11, 3, -1], [2, -5, 4, 0], [-32, 2, -5, 0], [-2, 5, 2, -4], [2, -8, -1, -6], [26, 4, -10, 0], [44, 1, 2, 0], [-30, -4, 1, -2], [24, -4, -1, -2], [-3, 0, -1, 3], [-10, -2, -1, 4], [-2, 0, 7, 2], [8, -2, 7, 0], [-18, -5, -1, 2], [6, -6, 7, 2], [-4, 8, -4, 0], [-33, 9, 1, 1], [17, -7, -5, -3], [8, 4, -2, 4], [11, 5, -5, 1], [-4, -10, -3, 0], [10, -4, -10, -2], [6, 5, 1, 2], [3, -7, 0, 1], [-34, -6, 7, 2], [11, -7, -3, -5], [-3, 3, -1, -1], [15, 5, 1, 5], [-6, -10, -12, -4], [14, -8, 6, 4], [18, -8, 2, -2], [12, 4, -4, -4], [19, 11, 1, 1], [28, 0, -4, 0], [-2, -4, 2, -4], [-24, 14, -1, 0], [25, 7, 5, 1], [34, 4, 0, 2], [-14, 4, -2, 2], [20, -8, 0, -2], [-32, -9, -9, 0], [-23, 9, 3, 3], [-8, 10, -2, -6], [-20, -5, -5, 4], [-22, 4, -4, -2], [10, -2, -1, -2], [33, 8, 3, -1], [34, -6, -2, -2], [5, -9, 2, 3], [4, 3, -12, 6], [-32, -4, -8, 0], [5, -5, -10, -1], [-22, 0, 0, -4], [-25, 5, -3, -3], [16, 4, 9, 2], [-6, 10, 7, 0], [-54, 5, 3, 2], [8, 3, 0, 2], [63, 1, 1, 1], [-14, -3, -8, -2], [-48, 6, -1, 0], [32, 0, -8, 0], [4, 6, 1, 4], [18, 4, -7, 6], [-8, -2, -8, -8], [-4, -5, 6, 4], [36, -1, -1, -4], [16, -4, 1, 4], [16, 2, -6, 2], [16, -10, 0, 4], [-30, -11, 2, 0], [6, 16, 5, 2], [12, 1, 0, -4], [-47, 7, -3, 3], [32, -5, 1, 4], [6, 7, 4, 6], [4, -2, -3, 4], [10, 7, 6, -4], [-32, -2, 2, 2], [-10, 0, -1, -2], [8, -3, -6, 2], [20, -2, -9, 0], [-4, 2, 4, -8], [0, 2, -4, -2], [26, -2, -1, 0], [-28, -4, -8, 0], [4, -14, -6, -2], [-28, 6, -2, -2], [-18, -3, 5, 2], [24, 4, 5, 2], [-26, -8, -6, -6], [-36, 2, -4, -4], [-18, 1, -2, -6], [22, -6, 4, 10], [4, 0, -6, 0], [-16, 8, 10, 2], [-6, 13, -4, 2], [6, -2, -3, 0], [-4, 2, -6, 2], [-6, -1, 8, -2], [-6, -11, -9, -6], [31, 7, 9, 3], [-6, 9, 7, 2], [-4, -8, -2, -6], [-42, 1, 2, 2], [-18, -14, 2, 2], [-12, -10, 3, 4], [24, 8, -6, -4], [28, 2, -8, 4], [34, -14, 1, -6], [17, 6, 7, -1], [-4, 4, -8, 4], [-9, 1, 1, -7], [-20, 5, -8, 2], [-4, 14, -2, -2], [-46, -4, 6, 2], [-8, -13, -4, 0], [6, 14, -10, -2], [4, 2, 6, 6], [12, -12, -1, -6], [21, -6, -1, -1], [-4, -4, -2, 6], [5, 7, -1, -5], [2, -8, -6, 6], [-4, -18, -3, 0], [4, 0, 2, 0], [-19, 19, 1, 5], [-12, 14, 3, 0], [-15, -11, 3, 1], [-32, -3, 11, -4], [-28, 8, -4, 2], [14, 4, 3, -6], [17, 3, 3, 9], [12, 12, -8, -2], [-40, 0, 11, 4], [32, -11, -4, -2], [18, -4, 0, -6], [13, -5, 11, -1], [28, -7, 2, 0], [-14, -18, 0, 4], [22, -10, 8, 0], [14, -14, 5, -8], [-6, 0, -2, -2], [-12, -7, 0, -6], [-24, 4, -6, -4], [25, 0, 7, 7], [-4, -6, -11, -4], [0, 2, -14, 2], [4, -14, 0, 4], [-42, 0, 0, 4], [6, 2, -8, 0], [28, -6, 5, 4], [-40, 4, 4, 0], [23, -10, 1, -7], [12, -2, 8, 4], [-54, -6, -3, 2], [-18, -16, -2, -2], [2, -12, 2, -6], [-36, 11, -4, 4], [-44, -4, 4, 4], [25, 7, 1, -1], [10, 8, -2, 4], [-16, -4, 8, 4], [-1, 22, -7, -3], [15, 9, -5, -3], [18, -14, -6, -2], [-18, 9, 11, 6], [23, 1, -1, 5], [-1, -7, -3, 3], [-2, 17, -4, 2], [-18, 0, 4, -8], [-3, 11, 3, 5], [0, 9, 8, 6], [-12, 22, -8, 0], [8, -16, -4, 0], [-16, 14, 3, 0], [34, 2, -2, 2], [-4, -8, 2, 2], [27, -1, 9, 5], [-8, 0, -10, -8], [-5, 17, -11, 3], [42, -11, -4, -6], [2, 12, 0, 2], [-28, 2, 2, -10], [10, 8, -4, -6], [30, -12, -10, -6], [22, 4, -3, 6], [42, 10, 1, -2], [30, 0, -2, 8], [-24, -9, 2, 0], [-6, 6, -6, 0], [2, -2, 8, -6], [-1, -9, 5, 3], [-12, -15, 1, 4], [4, 16, 3, 2], [-42, 6, 8, 6], [-8, -6, -5, -4], [-4, -11, 0, 2], [2, 0, -2, 2], [38, 4, -6, 8], [6, -6, -5, 2], [-54, 2, -2, -2], [6, -4, -8, 2], [27, -13, -11, -7], [-4, 4, -8, 2], [-12, 6, 8, 4], [-20, 0, -9, 8], [32, -1, -14, -2], [8, 20, -2, -6], [28, 4, 1, 8], [-6, -8, 12, -8], [-3, 11, 3, 11], [-6, 6, -3, 6], [42, -12, -7, -6], [-1, 25, -6, -3], [-5, -10, 13, 1], [-8, 2, -6, 2], [-28, 1, 1, 4], [40, 8, 6, 4], [7, 1, -5, -3], [18, 2, 0, -4], [-8, 9, 4, 6], [-30, -7, 0, -4], [-38, 0, -2, 0], [-4, 12, 9, 4], [69, -1, 3, 1], [-11, 3, -12, -5], [-26, -14, -5, 2], [30, 8, 2, 10], [-22, 15, -8, 2], [-20, 3, -10, -12], [24, -4, -4, -8], [-24, 6, -4, -4], [16, -18, 6, -2], [-6, 0, 7, -2], [-24, -17, -6, -2], [62, 2, 2, 2], [-30, -12, 0, 6], [5, -5, 0, -1]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_2898_a_Hecke(Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_2898_2_a_bh();".
// This may take a long time!  To see verbose output, uncomment the SetVerbose lines below.
// The precision argument determines an initial guess on how many Fourier coefficients to use.
// This guess is increased enough to uniquely determine the newform.
function MakeNewformModFrm_2898_2_a_bh(:prec:=4)
    chi := MakeCharacter_2898_a();
    f_vec := qexpCoeffs();
    Kf := Universe(f_vec);
    // SetVerbose("ModularForms", true);
    // SetVerbose("ModularSymbols", true);
    S := CuspidalSubspace(ModularForms(chi, 2));
    S := BaseChange(S, Kf);
    maxprec := NextPrime(2999) - 1;
    while true do
        trunc_vec := Vector(Kf, [0] cat [f_vec[i]: i in [1..prec]]);
        B := Basis(S, prec + 1);
        S_basismat := Matrix([AbsEltseq(g): g in B]);
        if Rank(S_basismat) eq Min(NumberOfRows(S_basismat), NumberOfColumns(S_basismat)) then
            S_basismat := ChangeRing(S_basismat,Kf);
            f_lincom := Solution(S_basismat,trunc_vec);
            f := &+[f_lincom[i]*Basis(S)[i] : i in [1..#Basis(S)]];
            return f;
        end if;
        error if prec eq maxprec, "Unable to distinguish newform within newspace";
        prec := Min(Ceiling(1.25 * prec), maxprec);
    end while;
end function;


// To make the Hecke irreducible modular symbols subspace (type ModSym)
// containing the newform, type "MakeNewformModSym_2898_2_a_bh();".
// This may take a long time!  To see verbose output, uncomment the SetVerbose line below.
// The default sign is -1.  You can change this with the optional parameter "sign".
function MakeNewformModSym_2898_2_a_bh( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_2898_a();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,2,sign)));
    Vf := Kernel([<5,R![24, -8, -18, 0, 1]>,<11,R![-48, -48, 6, 8, 1]>,<13,R![-24, -56, -30, 0, 1]>],Snew);
    return Vf;
end function;