
// Make newform 980.2.q.g in Magma, downloaded from the LMFDB on 20 April 2024.
// To make the character of type GrpDrchElt, type "MakeCharacter_980_q();"
// To make the character of type GrpDrchElt with Codomain the HeckeField, type "MakeCharacter_980_q_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_980_2_q_g();".
// 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_980_2_q_g();".
// 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 := [25, -5, -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], [-5, -4, 4, 1], [5, 4, 0, -1]];
    Rf_basisdens := [1, 1, 20, 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_980_q();"
function MakeCharacter_980_q()
    N := 980;
    order := 6;
    char_gens := [491, 197, 101];
    v := [6, 3, 2];
    // 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_980_q_Hecke();"
function MakeCharacter_980_q_Hecke(Kf)
    N := 980;
    order := 6;
    char_gens := [491, 197, 101];
    char_values := [[1, 0, 0, 0], [-1, 0, 0, 0], [-1, 0, 1, 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], [2, 0, -1, 0], [0, 0, 0, 1], [0, 0, 0, 0], [1, -2, 1, 1], [2, -2, -2, 2], [-3, 0, 1, -1], [1, -1, 0, 2], [-3, 2, -1, 0], [-1, 1, 1, 1], [1, -2, -1, 1], [5, -1, 4, 0], [7, 1, 1, 1], [-3, 1, 5, -1], [3, -1, 2, 0], [-1, 0, -1, -3], [1, -2, -1, 1], [-5, -2, 7, 4], [-6, 0, 1, -4], [2, 2, 2, 2], [5, 0, -3, -1], [3, 1, -4, -2], [-1, 3, -1, -3], [7, 0, -7, 0], [-4, 0, 8, 0], [-2, 4, -5, -2], [-5, 2, -3, 0], [1, 4, 5, 0], [-2, 4, -3, -2], [6, -2, -10, 2], [2, 4, -8, -4], [-15, 1, 14, -2], [-7, 0, 7, 7], [0, -4, -4, -4], [1, -2, 1, 4], [-1, 2, 17, -1], [-5, 0, 1, -3], [1, -3, -2, 0], [5, -3, -7, 3], [-5, 9, 4, 0], [-1, 2, -3, -1], [21, -1, -1, -1], [-13, 3, 10, -6], [-7, 0, 7, 7], [-12, 4, 20, -4], [-1, 2, -13, -1], [6, -6, -6, -6], [-2, 4, 0, -4], [15, 0, -9, -3], [1, -1, 0, 2], [9, 1, 10, 0], [6, 2, 2, 2], [3, -6, -3, 3], [14, -2, -2, -2], [-9, -3, -12, 0], [-16, 0, 5, -6], [-2, 4, 23, -2], [-3, 3, 0, -6], [19, 0, -9, 1], [6, 0, 0, 0], [-5, 0, -1, -7], [-4, 0, 8, 0], [3, 7, -13, -7], [-3, 6, 3, -3], [11, -11, 0, 0], [-11, 5, -6, 0], [-5, -3, 8, 6], [6, -2, -10, 2], [14, 0, -7, 0], [-7, -1, -1, -1], [17, 0, -7, 3], [15, 5, -20, -10], [12, 0, -5, 2], [5, -1, 4, 0], [2, -6, -6, -6], [-1, -6, -7, 0], [5, -10, 11, 5], [7, 1, 8, 0], [-3, 0, 3, 0], [4, -8, 3, 4], [0, 4, 4, 4], [-1, 1, 1, 1], [5, -10, -3, 5], [14, -2, -26, 2], [-11, -3, 14, 6], [-7, 0, -7, 0], [13, 3, 3, 3], [-3, -5, -8, 0], [14, 0, 0, 0], [3, -1, -5, 1], [3, -8, -5, 0], [-3, 6, 3, -3], [21, 0, -7, 7], [-22, 2, 2, 2], [23, -5, -18, 10], [1, -11, 9, 11], [23, -2, -21, 4], [3, -6, -3, 3], [-5, -1, -6, 0], [9, 2, -11, -4], [-11, 13, 9, -13], [9, 0, -5, -1], [-6, 0, 7, 8], [-13, 5, 8, -10], [-1, 2, -3, -1], [7, 0, -3, 1], [-2, 8, -4, -8], [-17, 3, -14, 0], [1, -2, 1, 1], [-14, 0, 0, 0], [-1, -10, -11, 0], [-5, 0, -5, -15], [4, 8, -16, -8], [7, -14, -21, 7], [20, -4, -4, -4], [4, -8, -15, 4], [-10, 16, 4, -16], [-16, 0, 11, 6], [5, -15, -10, 0], [34, -2, -2, -2], [2, -4, -9, 2], [-4, -8, 16, 8], [23, -5, 18, 0], [-2, 0, 5, 8], [9, 5, -14, -10], [-1, -3, -3, -3], [-19, 2, 17, -4], [9, 5, -14, -10], [-7, 5, 9, -5], [-21, 1, -20, 0], [-7, 14, 9, -7], [-9, 3, 15, -3], [19, -1, -18, 2], [-10, -6, 26, 6], [-7, 7, 0, -14], [-14, 0, 0, 0], [-39, 0, 21, 3], [2, 0, -1, 0], [-20, -4, 44, 4], [-8, 16, 17, -8], [-14, -2, -2, -2], [-1, 5, -4, -10], [-8, 0, 13, 18], [21, -7, -35, 7], [7, -14, 21, 7], [28, -4, -4, -4], [10, -10, -10, 10], [-41, 0, 21, 1], [-19, 5, 14, -10], [-11, -2, -13, 0], [17, 5, 22, 0], [7, -11, -11, -11], [18, 8, -44, -8], [-9, 18, 9, 0], [2, 0, 9, 20], [-12, 4, 4, 4], [-17, -7, 24, 14], [31, 4, -35, -8], [0, 8, -8, -8], [-1, 2, 1, -1], [-3, -12, -15, 0], [-8, 12, 4, -12], [3, -1, -5, 1], [-7, -7, 14, 14], [-27, 0, 15, 3], [48, 0, -25, -2], [-9, 18, 5, -9], [-3, 0, 1, -1]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_980_q_Hecke(Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_980_2_q_g();".
// 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_980_2_q_g(:prec:=4)
    chi := MakeCharacter_980_q();
    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_980_2_q_g();".
// 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_980_2_q_g( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_980_q();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,2,sign)));
    Vf := Kernel([<3,R![3, -3, 1]>,<11,R![144, 36, 21, -3, 1]>,<19,R![196, 14, 15, -1, 1]>],Snew);
    return Vf;
end function;