
// Make newform 605.2.a.i in Magma, downloaded from the LMFDB on 19 April 2024.
// To make the character of type GrpDrchElt, type "MakeCharacter_605_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_605_2_a_i();".
// 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_605_2_a_i();".
// 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 := [5, 5, -4, -2, 1];
        Kf := NumberField(Polynomial([elt : elt in poly]));
        AssignNames(~Kf, ["nu"]);
    end if;
    Rf_num := [[1, 0, 0, 0], [0, 1, 0, 0], [-3, -1, 1, 0], [0, -3, -1, 1]];
    Rf_basisdens := [1, 1, 1, 1];
    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_605_a();"
function MakeCharacter_605_a()
    N := 605;
    order := 1;
    char_gens := [122, 486];
    v := [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_605_a_Hecke(Kf)
    return MakeCharacter_605_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, -1], [0, -1, 0, 0], [1, 0, 0, 0], [-3, 0, -1, 1], [0, 0, 0, 0], [-1, 0, 2, -1], [-1, 1, 0, 1], [-4, 1, -1, 0], [-2, 3, 3, 1], [0, 1, -3, 0], [1, -2, -2, 1], [-1, 1, 2, -3], [3, -1, 0, 3], [-3, -2, 2, 1], [1, -3, 1, -1], [-2, -1, 0, 1], [-5, 2, -3, -3], [-2, 2, 1, -2], [-2, 0, -2, -3], [-6, -2, -8, 3], [4, 2, 6, -1], [2, -3, 5, -2], [-5, -1, -3, -1], [3, -2, 6, -4], [-1, 2, -2, -2], [8, 1, 6, 1], [-5, 4, -2, 2], [1, -7, 6, -2], [-2, -2, 0, -3], [-1, 1, -5, 7], [-12, -1, -12, 2], [5, 4, 6, 1], [-9, -2, -9, 1], [2, -9, -2, 3], [10, -5, 0, 0], [-1, 1, 4, 0], [1, -2, -4, 1], [-7, -1, -1, 2], [-8, 0, 3, -3], [-8, 0, -13, 5], [5, 6, 2, 0], [9, -2, -2, -3], [4, -4, 12, -1], [-11, 3, 1, 1], [4, -7, 2, -7], [-1, -3, -7, 4], [-14, 4, 0, -1], [6, 2, 0, -2], [-11, 7, 8, 0], [-1, 5, 13, 5], [5, 0, 7, 1], [8, -1, 17, -3], [-4, -4, -13, 6], [0, 1, -4, -8], [-11, 1, -13, 7], [-2, 8, 4, 1], [-3, 0, 0, -1], [-2, 10, 1, -1], [4, -2, -7, 12], [3, -3, -13, 2], [-16, 0, -9, 5], [-13, 0, -11, -7], [-14, 5, -8, 1], [-5, 5, 3, 3], [13, -5, 5, 8], [0, 1, 1, 5], [-10, 0, -8, 4], [3, 4, -7, 2], [-4, 2, -1, 3], [-5, 6, -10, -3], [-17, 0, -5, 3], [5, -8, -4, -2], [24, 1, 5, 4], [2, -7, 10, -2], [-4, 4, 7, -2], [4, 5, -8, 3], [-1, -10, -4, 2], [11, -6, 7, 2], [-1, 13, -6, 1], [-19, 10, -5, -8], [-7, -7, 2, -5], [2, -6, 7, 1], [6, 1, -6, -1], [-1, -5, 2, -12], [-1, -5, -3, -14], [24, -8, -3, -3], [-11, 5, -6, -6], [19, -4, 11, 0], [16, -5, -1, -3], [0, 9, -8, -2], [0, 0, 5, -6], [2, 9, -23, 5], [-11, 3, 2, 6], [6, -6, 6, 3], [9, -1, 10, 6], [-4, 1, 5, -3], [-20, 4, -3, -9], [20, -6, 17, -3], [-17, 13, 1, -6], [-6, -12, -5, -2], [-19, 13, -9, -2], [20, -11, -5, -6], [-14, 5, -21, -4], [7, 11, 1, 5], [-7, 6, -2, -1], [2, 7, 3, 9], [-22, 11, -1, -12], [3, 9, -5, 2], [-23, 3, 1, -1], [11, -14, 6, -13], [10, -7, 11, -9], [9, -13, -9, -1], [-6, -7, 14, -11], [12, 1, 4, 12], [-3, 0, 24, -4], [5, 2, 2, -12], [-20, -1, 7, -2], [7, 0, 19, -16], [-11, 3, -27, 3], [23, 0, 23, 3], [-1, 11, 13, -12], [-13, -7, -18, 6], [9, -10, -8, 2], [1, 3, -1, -9], [-11, 5, -16, 20], [9, -13, 12, -11], [-8, -3, -11, 4], [1, -1, 7, -7], [-15, -14, -24, 10], [8, -8, 25, -2], [-21, -1, 1, -10], [-8, 10, 4, 8], [-17, -8, 19, -8], [-2, 10, -16, -4], [11, -5, 17, 9], [-13, 2, -10, 18], [10, -14, 27, -3], [-10, -2, 19, -12], [26, -5, 6, -10], [7, -2, 30, -10], [-18, -5, 10, 3], [11, -6, 1, 13], [-12, -2, -17, 6], [-14, 19, -4, 5], [9, 5, 22, 11], [3, 7, 5, 10], [-6, -13, -13, 8], [-6, 15, 12, 12], [-7, -7, 5, -3], [27, 2, 21, -6], [7, 0, 10, -20], [7, -9, 8, 4], [-9, -6, -11, -7], [4, -9, -10, -4], [21, -10, 2, 9], [26, 6, 6, 4], [14, -6, -4, 20], [9, -17, -4, 8], [22, 11, 11, -9], [-5, 5, -9, 18], [18, -8, 11, 3], [-18, -1, 0, 10], [-19, 2, -37, -1], [36, 0, 5, 3], [12, -5, -16, -1], [-11, 8, 1, 0], [-29, 9, -29, -5], [1, 12, 5, -3]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_605_a_Hecke(Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_605_2_a_i();".
// 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_605_2_a_i(:prec:=4)
    chi := MakeCharacter_605_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(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_605_2_a_i();".
// 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_605_2_a_i( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_605_a();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,2,sign)));
    Vf := Kernel([<2,R![-1, -11, -3, 3, 1]>,<3,R![5, -5, -4, 2, 1]>],Snew);
    return Vf;
end function;