
// Make newform 6384.2.a.g in Magma, downloaded from the LMFDB on 26 April 2024.
// To make the character of type GrpDrchElt, type "MakeCharacter_6384_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_6384_2_a_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_6384_2_a_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
        Kf := Rationals();
    end if;
    return [Kf!elt[1] : elt in input];
end function;


// To make the character of type GrpDrchElt, type "MakeCharacter_6384_a();"
function MakeCharacter_6384_a()
    N := 6384;
    order := 1;
    char_gens := [799, 4789, 2129, 913, 1009];
    v := [1, 1, 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_6384_a_Hecke(Kf)
    return MakeCharacter_6384_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 := [[0], [-1], [-2], [1], [2], [2], [-4], [-1], [0], [-6], [10], [0], [-6], [4], [-6], [-6], [12], [10], [2], [-8], [-6], [-16], [12], [10], [-12], [-10], [14], [4], [4], [2], [-8], [-8], [2], [-4], [0], [-8], [6], [8], [0], [14], [-24], [2], [0], [22], [-8], [4], [-26], [6], [-12], [-10], [-2], [-12], [-24], [-24], [6], [-8], [18], [8], [6], [-30], [12], [-30], [-20], [-10], [-30], [-18], [6], [-26], [-10], [-10], [-24], [-12], [16], [4], [-2], [-16], [0], [-14], [-10], [-28], [20], [36], [-40], [-20], [34], [10], [14], [-10], [10], [32], [12], [26], [-4], [-30], [-12], [-26], [-30], [18], [28], [26], [-30], [0], [-4], [10], [32], [-30], [0], [4], [16], [16], [26], [-22], [-26], [4], [-8], [-26], [4], [42], [-12], [32], [22], [34], [30], [-20], [-28], [0], [46], [-42], [-28], [-34], [-12], [8], [-20], [-6], [-40], [-30], [-46], [24], [14], [6], [-44], [-12], [24], [-16], [14], [32], [-6], [10], [52], [56], [32], [-24], [-12], [-36], [22], [56], [-24], [-28], [-2], [10], [42], [-14], [16], [12], [38], [-44], [-20], [22], [6], [-14], [-20], [-14], [-56], [-58], [18], [36], [-52], [4], [-50], [10], [24], [36], [-60], [62], [24], [-6], [8], [-4], [10], [62], [60], [42], [34], [-10], [6], [26], [-50], [58], [-56], [-54], [-14], [-46], [-2], [60], [16], [54], [20], [44], [-38], [-40], [-42], [6], [-16], [-12], [-8], [-8], [-16], [-62], [64], [8], [36], [-26], [-14], [64], [-12], [-2], [6], [-64], [6], [-18], [2], [64], [-60], [-70], [-68], [22], [50], [36], [-34], [72], [24], [-76], [40], [-32], [14], [30], [-52], [-12], [-54], [12], [58], [-4], [44], [12], [14], [-54], [-10], [48], [-26], [14], [64], [-48], [38], [-2], [72], [60], [-6], [28], [-58], [16], [2], [74], [-38], [40], [56], [64], [30], [64], [50], [8], [28], [-40], [-42], [38], [-28], [36], [30], [-2], [-28], [-42], [-48], [12], [34], [20], [-24], [34], [-50], [-78], [-20], [-12], [-66], [-54], [24], [-64], [20], [74], [-28], [14], [-60], [-82], [14], [-60], [22], [-2], [84], [0], [68], [0], [86], [-2], [32], [-74], [18], [52], [62], [-16], [70], [24], [80], [12], [-86], [-62], [44], [-36], [8], [-92], [-16], [-78], [-58], [-84], [44], [18], [30], [72], [66], [0], [-38], [-38], [-24], [-82], [-40], [-2], [80], [46], [-68], [50], [82], [24], [-18], [-24], [-62], [36], [0], [84], [52], [-74], [58], [-16], [-58], [-18], [28], [12], [90], [32], [-34], [52], [88], [-78], [-8], [-48], [-10], [-90], [-88], [66], [-44], [4], [8], [34], [20], [-16], [-2], [6], [-30], [36], [24], [50], [-86], [-10], [78], [-96], [-10], [78], [-52], [70], [-70], [-20], [-58], [-86], [48], [-100], [24], [16], [-68], [-96], [22], [-22], [8], [-70], [68], [4], [90], [46], [-48], [-76], [-44], [-50], [-12], [-18], [-4], [86]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_6384_a_Hecke(Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_6384_2_a_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_6384_2_a_g(:prec:=1)
    chi := MakeCharacter_6384_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_6384_2_a_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_6384_2_a_g( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_6384_a();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,2,sign)));
    Vf := Kernel([<5,R![2, 1]>,<11,R![-2, 1]>,<13,R![-2, 1]>,<17,R![4, 1]>,<23,R![0, 1]>],Snew);
    return Vf;
end function;