
// Make newform 33.6.a.a in Magma, downloaded from the LMFDB on 24 April 2024.
// To make the character of type GrpDrchElt, type "MakeCharacter_33_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_33_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_33_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_33_a();"
function MakeCharacter_33_a()
    N := 33;
    order := 1;
    char_gens := [23, 13];
    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_33_a_Hecke(Kf)
    return MakeCharacter_33_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 := [[-2], [-9], [46], [148], [121], [574], [-722], [2160], [-2536], [4650], [5032], [8118], [-5138], [8304], [24728], [-28746], [-5860], [-53658], [30908], [-69648], [-18446], [-25300], [-17556], [132570], [70658], [-101998], [130904], [-141612], [-239810], [-42726], [51788], [53652], [-228862], [374920], [-65830], [154052], [287678], [105124], [150528], [-2166], [672780], [-526778], [-305608], [116434], [-247742], [-513360], [-620688], [-1318016], [-887412], [-237450], [-914706], [1408920], [-826358], [-1603868], [397618], [2131664], [-725810], [-1467868], [1520998], [464382], [-415136], [-2593206], [-930832], [2485272], [1317194], [2255398], [-3170708], [1276298], [3693028], [1709190], [4368594], [-3512840], [-2152592], [-2242466], [-2409860], [-1010656], [1277790], [5453998], [-1489798], [-4398990], [-280420], [817462], [1885992], [5840674], [-509540], [4102684], [513410], [1227378], [-6409998], [6630304], [-4147692], [-5051320], [2662208], [-5546588], [-6820], [-451136], [393390], [3284322], [-1682656], [9481582], [-6092392], [8495938], [-7022156], [9418470], [7296992], [-3295902], [4398268], [9217814], [3771400], [4197242], [-1001332], [-7382386], [-15402462], [-7124020], [11669632], [-11027118], [-9560236], [-10994152], [-295346], [-16561340], [1970422], [-1637326], [-6358782], [11103284], [17018852], [15802082], [12483350], [2007240], [6973008], [-23496546], [-13990120], [24274504], [15365992], [20760518], [5838102], [-13919710], [-4178826], [9667048], [-5798842], [-19254330], [-13193768], [13377922], [-18861336], [16267988], [-21809810], [11777080], [-14399266], [6276038], [-4717380], [7539264], [-10433082], [39107642], [12928204], [33646568], [-41962932], [-1925208], [-17248100], [2511450], [17985338], [-32258598], [44165868], [18748774], [10867348], [-47912308], [40138458], [3226824], [-5953448], [32078318]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_33_a_Hecke(Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_33_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_33_6_a_a(:prec:=1)
    chi := MakeCharacter_33_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_33_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_33_6_a_a( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_33_a();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,6,sign)));
    Vf := Kernel([<2,R![2, 1]>],Snew);
    return Vf;
end function;