
// Make newform 7488.2.a.bg in Magma, downloaded from the LMFDB on 14 December 2025.
// To make the character of type GrpDrchElt, type "MakeCharacter_7488_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_7488_2_a_bg();".
// 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_7488_2_a_bg();".
// 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_7488_a();"
function MakeCharacter_7488_a()
    N := 7488;
    order := 1;
    char_gens := [703, 6085, 5825, 5761];
    v := [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_7488_a_Hecke( : Kf := Kf)
    return MakeCharacter_7488_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]];
    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], [2], [4], [-1], [6], [-6], [0], [-2], [-6], [-10], [-8], [-12], [-12], [-6], [0], [-2], [-2], [8], [14], [4], [8], [-4], [14], [-18], [4], [-4], [2], [10], [-8], [20], [-8], [0], [-12], [-10], [-18], [-10], [12], [-18], [12], [-10], [0], [-6], [0], [-16], [28], [26], [4], [10], [18], [16], [-10], [-12], [-14], [32], [-10], [2], [-22], [0], [0], [-12], [-22], [16], [-6], [0], [14], [18], [4], [-18], [8], [-36], [-8], [26], [18], [36], [2], [22], [12], [-2], [-12], [2], [-28], [-34], [-4], [4], [20], [-34], [32], [34], [28], [-40], [-6], [-20], [22], [24], [24], [10], [40], [2], [-8], [-36], [36], [18], [-8], [-22], [0], [-20], [-32], [-22], [40], [46], [-24], [-30], [6], [-18], [-34], [16], [30], [20], [6], [-26], [-30], [-4], [30], [-30], [-22], [0], [16], [42], [10], [-40], [-4], [-10], [-24], [-30], [12], [-22], [18], [-14], [34], [20], [-12], [-12], [38], [56], [-18], [-22], [-44], [12], [14], [2], [-8], [-40], [-48], [32], [-36], [32], [-2], [28], [-32], [34], [2], [12], [12], [-32], [-32], [50], [30], [-26], [-52], [30], [0], [-42], [-12], [6], [42], [-36], [-44], [-30], [10], [44], [38], [-28], [20], [-6], [-18], [-46], [-2], [20], [-2], [24], [32], [36], [36], [-46], [-38], [-46], [4], [56], [40], [-56], [-14], [-50], [40], [-62], [-46], [36], [-60], [-32], [46], [2], [-52], [-20], [20], [-14], [4], [38], [-24], [68], [-70], [10], [-60], [34], [-68], [-38], [54], [0], [64], [0], [-66], [-8], [-26], [30], [-56], [-48], [22], [28], [12], [-24], [-8], [-56], [4], [54], [36], [-8], [-46], [-24], [-22], [48], [2], [40], [-48], [26], [46], [4], [74], [26], [2], [34], [-72], [-36], [-38], [-22], [-60], [52], [8], [0], [2], [-82], [14], [-2], [14], [68], [42], [70], [36], [-58], [50], [-68], [-32], [-38], [-64], [30], [10], [48], [-2], [-12], [46], [2], [2], [-12], [-52], [0], [-2], [58], [48], [-6], [12], [34], [-86], [-16], [-44], [-76], [-40], [-2], [-4], [2], [0], [-30], [-64], [32], [-6], [-44], [-28], [-62], [84], [4], [-74], [62], [-12], [-22], [26], [38], [-36], [30], [46], [54], [-72], [-82], [-70], [-66], [44], [36], [10], [40], [-74], [-48], [86], [68], [6], [2], [4], [-12], [-16], [-68], [-38], [14], [36], [-70], [-42], [78], [12], [-56], [-10], [-54], [36], [52], [90], [-36], [-42], [-50], [0], [-44], [76], [-10], [72], [-2], [78], [-52], [-12], [-36], [58], [68], [66], [80], [-64], [2], [-50], [-26], [60], [80], [50], [-84], [14], [-48], [-90], [-18], [82], [72], [-34], [36], [-92], [-20], [60], [-74], [14], [78], [-20], [8], [62], [22], [98], [84], [0], [-28], [-22], [44], [-6], [4], [34], [-62], [-60], [-44], [-78], [50], [96], [-76], [68], [48], [-10], [78], [24], [4], [26], [-20], [-36], [-84], [-2], [16]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_7488_a_Hecke( : Kf := Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_7488_2_a_bg();".
// 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_7488_2_a_bg(:prec:=1)
    chi := MakeCharacter_7488_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_7488_2_a_bg();".
// 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_7488_2_a_bg( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_7488_a();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,2,sign)));
    Vf := Kernel([<5,R![0, 1]>,<7,R![-2, 1]>,<11,R![-4, 1]>,<17,R![-6, 1]>,<19,R![6, 1]>,<29,R![2, 1]>],Snew);
    return Vf;
end function;