
// Make newform 287.2.e.b in Magma, downloaded from the LMFDB on 25 April 2024.
// To make the character of type GrpDrchElt, type "MakeCharacter_287_e();"
// To make the character of type GrpDrchElt with Codomain the HeckeField, type "MakeCharacter_287_e_Hecke();"
// To make the coeffs of the qexp of the newform in the Hecke field type "qexpCoeffs();"
// To make the newform (type ModFrm), type "MakeNewformModFrm_287_2_e_b();".
// 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_287_2_e_b();".
// 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 := [9, 3, 4, -1, 1];
        Kf := NumberField(Polynomial([elt : elt in poly]));
        AssignNames(~Kf, ["nu"]);
    end if;
    Rf_num := [[1, 0, 0, 0], [0, 1, 0, 0], [-3, -4, 4, -1], [7, 0, 0, 1]];
    Rf_basisdens := [1, 1, 12, 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_287_e();"
function MakeCharacter_287_e()
    N := 287;
    order := 3;
    char_gens := [206, 211];
    v := [2, 3];
    // 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;

// To make the character of type GrpDrchElt with Codomain the HeckeField, type "MakeCharacter_287_e_Hecke();"
function MakeCharacter_287_e_Hecke(Kf)
    N := 287;
    order := 3;
    char_gens := [206, 211];
    char_values := [[0, 0, 1, 0], [1, 0, 0, 0]];
    assert UnitGenerators(DirichletGroup(N)) eq char_gens;
    values := ConvertToHeckeField(char_values : pass_field := true, Kf := Kf); // the value of chi on the gens as elements in the Hecke field
    F := Universe(values);// the Hecke field
    chi := DirichletCharacterFromValuesOnUnitGenerators(DirichletGroup(N,F),values);
    return chi;
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 := [[0, 0, 0, 0], [0, -1, 0, 0], [-1, 1, -1, 1], [1, 0, 3, 0], [2, 1, 2, 0], [-1, 0, 0, 1], [-3, 3, -3, 0], [2, -2, 1, -2], [2, -2, -1, -2], [3, 0, 0, -2], [0, 1, 0, 0], [-4, 4, -2, 4], [-1, 0, 0, 0], [-7, 0, 0, 2], [0, 0, -9, 0], [-3, -3, -3, 0], [-5, 2, -5, 0], [-4, 4, -2, 4], [2, 2, 2, 0], [3, 0, 0, -6], [-7, -1, -7, 0], [8, -8, 1, -8], [9, 0, 0, -2], [2, -2, 5, -2], [8, 0, 0, -1], [7, 2, 7, 0], [-4, 4, -11, 4], [3, -3, 0, -3], [-4, -1, -4, 0], [0, 0, 0, 6], [2, 0, 0, -9], [1, -1, 4, -1], [15, -6, 15, 0], [-1, 0, 0, 3], [6, -6, 12, -6], [5, -7, 5, 0], [11, -4, 11, 0], [9, -9, 5, -9], [-3, 0, 0, -6], [5, -5, -4, -5], [16, -1, 16, 0], [8, 0, 0, -10], [1, -1, -17, -1], [12, -2, 12, 0], [0, 0, 0, -3], [9, 4, 9, 0], [-1, 0, 0, 7], [2, 0, 0, -5], [-22, 4, -22, 0], [9, -9, 17, -9], [-11, 11, -2, 11], [15, 0, 0, -6], [10, -6, 10, 0], [-18, 0, 0, 3], [-3, 3, 9, 3], [-14, -1, -14, 0], [-5, -1, -5, 0], [-6, 6, 11, 6], [-14, 9, -14, 0], [0, 0, 0, 5], [9, -8, 9, 0], [-21, 0, 0, -4], [-13, 0, 0, 15], [-9, -6, -9, 0], [-9, 9, -1, 9], [3, -3, -9, -3], [-10, 10, -23, 10], [-4, 0, 0, 9], [24, -6, 24, 0], [-13, 0, 0, -6], [-3, 12, -3, 0], [12, -12, 0, -12], [26, -4, 26, 0], [-11, 11, -3, 11], [-13, 0, 0, -4], [-4, 4, -4, 4], [-16, 7, -16, 0], [9, -9, -16, -9], [2, -2, 11, -2], [28, 0, 28, 0], [-21, 0, 0, 7], [8, 0, 0, 3], [-17, 5, -17, 0], [32, 0, 0, -2], [-4, 4, 28, 4], [-7, 7, -10, 7], [24, 0, 0, -12], [10, -10, 3, -10], [-9, 0, 0, 0], [-16, 0, 0, -1], [-15, 15, -3, 15], [13, -19, 13, 0], [30, 1, 30, 0], [-3, 0, 0, 7], [-16, 16, -20, 16], [21, 0, 0, -6], [-9, 9, 3, 9], [2, -20, 2, 0], [0, 0, 17, 0], [-4, 4, -32, 4], [20, 0, 0, -9], [-9, 0, -9, 0], [-19, 4, -19, 0], [14, -14, -4, -14], [-1, -10, -1, 0], [-16, 20, -16, 0], [12, 0, 0, -18], [-4, 4, 8, 4], [11, -2, 11, 0], [-7, 0, 0, -17], [-6, 6, -10, 6], [7, 0, 7, 0], [3, 0, 0, 15], [-15, -5, -15, 0], [-22, 0, 0, 16], [33, 0, 33, 0], [8, 0, 0, 0], [-12, 12, -12, 0], [-6, 6, 24, 6], [-12, 0, 0, 14], [-34, -4, -34, 0], [-16, 0, 0, 16], [0, 0, -27, 0], [-37, 4, -37, 0], [-1, 1, -20, 1], [6, 0, 0, 16], [-2, 2, -27, 2], [7, -7, -14, -7], [-22, 0, 0, 15], [14, -14, -17, -14], [11, -4, 11, 0], [6, 0, 0, -21], [13, -13, -15, -13], [-16, 0, 0, 20], [-3, 3, 21, 3], [-7, 0, 0, -10], [-19, 4, -19, 0], [-11, -6, -11, 0], [-21, 0, 0, 6], [-21, -6, -21, 0], [-4, 0, 0, -11], [-19, 19, -16, 19], [24, -5, 24, 0], [-30, 0, 0, -6], [13, -6, 13, 0], [-3, 0, 0, 2], [11, 0, 0, 10], [-37, -5, -37, 0], [5, -5, 28, -5], [16, -16, 19, -16], [14, -14, 1, -14], [42, 0, 0, -3], [-10, 0, 0, -19], [-4, 4, 8, 4], [41, -10, 41, 0], [-15, 0, 0, 2], [-2, 2, -24, 2], [10, -10, -32, -10], [-4, 0, 0, 20], [0, 18, 0, 0], [-4, 4, -49, 4], [0, 0, 0, 15], [-46, 0, 0, 5], [19, -19, 10, -19], [9, -12, 9, 0], [36, -15, 36, 0], [23, -7, 23, 0], [8, 20, 8, 0]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_287_e_Hecke(Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_287_2_e_b();".
// 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_287_2_e_b(:prec:=4)
    chi := MakeCharacter_287_e();
    f_vec := qexpCoeffs();
    Kf := Universe(f_vec);
    // SetVerbose("ModularForms", true);
    // SetVerbose("ModularSymbols", true);
    S := CuspidalSubspace(ModularForms(chi, 2));
    S := BaseChange(S, Kf);
    maxprec := NextPrime(997) - 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_287_2_e_b();".
// 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_287_2_e_b( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_287_e();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,2,sign)));
    Vf := Kernel([<2,R![0, 1]>],Snew);
    return Vf;
end function;