
// Make newform 24.6.a.a in Magma, downloaded from the LMFDB on 25 April 2024.
// To make the character of type GrpDrchElt, type "MakeCharacter_24_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_24_6_a_a();".
// 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_24_6_a_a();".
// 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_24_a();"
function MakeCharacter_24_a()
    N := 24;
    order := 1;
    char_gens := [7, 13, 17];
    v := [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_24_a_Hecke(Kf)
    return MakeCharacter_24_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 := 6;
    raw_aps := [[0], [-9], [-34], [-240], [-124], [46], [1954], [-1924], [2840], [-8922], [-4648], [-4362], [-2886], [11332], [7008], [-22594], [-28], [-6386], [-39076], [-54872], [21034], [26632], [56188], [64410], [-116158], [-66834], [64000], [-15084], [-39698], [155154], [52072], [159964], [-262278], [253524], [355630], [-1024], [-59954], [-341556], [5016], [-228666], [161388], [-291690], [-55680], [-176254], [-374610], [-637760], [-904628], [619048], [-1469748], [-3290], [935402], [-875600], [-959214], [318868], [1714690], [-1110280], [-398378], [1441976], [117238], [-1675142], [1924676], [1280622], [-2263188], [247848], [-1823910], [2856294], [-147148], [-3247278], [-1556748], [4032174], [1793986], [1552776], [-3115448], [-630682], [48404], [1741824], [-3068194], [5359838], [-2764734], [-1208934], [-4380084], [-922810], [6126784], [-1763150], [3859056], [-4393964], [-793390], [7043018], [7430054], [-4105672], [3398172], [2781328], [-2067344], [-7659756], [-386580], [-2573256], [360678], [-1559078], [-9182204], [-6677730], [8896556], [-4460698], [6376604], [5511434], [1354308], [-5007358], [2699636], [13103474], [-5228040], [10224826], [8816840], [11359958], [-4773558], [-2559308], [-8419808], [-12149422], [-10896756], [13216552], [16591494], [-2293716], [-719194], [8646946], [-16959202], [18710468], [-11620420], [22349670], [10235270], [-17033920], [-16228032], [-21749506], [19619996], [17401784], [-26269272], [-5703562], [-21376214], [-2015230], [-12767442], [-27238436], [-7667242], [-10554086], [-1328828], [-6159330], [10073408], [-6491516], [-19353602], [-27862200], [10765094], [12243882], [-1386636], [-10985632], [8177982], [4665202], [38220092], [-7721720], [43313668], [3444560], [-43707296], [-41302190], [9574602], [8716230], [-13060500], [11387466], [46271072], [16320612], [-19521342], [-43396248], [38351800], [-7822058]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_24_a_Hecke(Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_24_6_a_a();".
// 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_24_6_a_a(:prec:=1)
    chi := MakeCharacter_24_a();
    f_vec := qexpCoeffs();
    Kf := Universe(f_vec);
    // SetVerbose("ModularForms", true);
    // SetVerbose("ModularSymbols", true);
    S := CuspidalSubspace(ModularForms(chi, 6));
    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_24_6_a_a();".
// 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_24_6_a_a( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_24_a();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,6,sign)));
    Vf := Kernel([<5,R![34, 1]>],Snew);
    return Vf;
end function;