
// Make newform 3136.2.a.ba in Magma, downloaded from the LMFDB on 25 April 2024.
// To make the character of type GrpDrchElt, type "MakeCharacter_3136_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_3136_2_a_ba();".
// 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_3136_2_a_ba();".
// 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_3136_a();"
function MakeCharacter_3136_a()
    N := 3136;
    order := 1;
    char_gens := [1471, 197, 1473];
    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_3136_a_Hecke(Kf)
    return MakeCharacter_3136_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], [2], [2], [0], [-4], [6], [4], [6], [-4], [6], [4], [6], [-4], [-12], [12], [-6], [6], [-6], [-12], [8], [0], [0], [6], [16], [12], [2], [-4], [4], [-2], [6], [12], [6], [6], [-14], [18], [-12], [-18], [-12], [-12], [-10], [4], [6], [-8], [-18], [-6], [-12], [-12], [24], [-18], [6], [6], [-28], [12], [-6], [-16], [-8], [-2], [16], [-30], [6], [-18], [26], [6], [0], [12], [18], [-12], [-22], [4], [30], [8], [-4], [-24], [-14], [-12], [12], [6], [6], [18], [-36], [-30], [-30], [-20], [12], [0], [-4], [-30], [-26], [-26], [24], [30], [36], [12], [-4], [-36], [24], [-26], [-28], [38], [-6], [-12], [18], [-6], [-6], [36], [24], [-6], [-8], [32], [0], [0], [-2], [-30], [-10], [48], [18], [-6], [-12], [-42], [4], [-30], [-18], [22], [-28], [-26], [-42], [-10], [-12], [28], [18], [-12], [-20], [-36], [-34], [-28], [-12], [10], [14], [-2], [54], [38], [18], [24], [20], [42], [12], [6], [44], [-30], [-40], [-50], [-16], [-36], [-36], [-36], [20], [24], [20], [0], [2], [-28], [-6], [12], [6], [-18], [-36], [-48], [42], [30], [14], [-20], [-18], [-8], [6], [-12], [56], [-12], [30], [56], [-54], [60], [18], [6], [40], [20], [62], [2], [-10], [6], [60], [-24], [20], [12], [38], [28], [-40], [-6], [54], [32], [48], [18], [12], [18], [0], [6], [-22], [-36], [-68], [-18], [18], [2], [-38], [-12], [-18], [0], [36], [-24], [4], [16], [-42], [14], [-32], [18], [36], [6], [30], [-32], [-28], [8], [44], [-58], [-6], [24], [-6], [6], [0], [-60], [18], [44], [-24], [44], [70], [24], [-30], [16], [-60], [-16], [78], [12], [64], [-22], [-40], [64], [0], [-22], [20], [30], [42], [58], [12], [36], [-4], [-54], [-30], [-52], [26], [42], [-16], [36], [54], [6], [12], [24], [60], [0], [-56], [-68], [18], [-18], [78], [24], [24], [12], [-6], [-58], [-28], [34], [-6], [44], [56], [-30], [-66], [66], [-18], [10], [-58], [48], [-34], [-78], [10], [60], [-66], [72], [-4], [12], [-2], [-76], [-30], [20], [-30], [-24], [6], [78], [-36], [64], [0], [42], [-40], [-48], [30], [90], [6], [-70], [48], [6], [60], [36], [-66], [52], [30], [-62], [-42], [44], [-54], [-60], [54], [-2], [-56], [72], [-52], [26], [-54], [-10], [48], [54], [-68], [-18], [-12], [72], [-22], [-30], [-54], [-30], [12], [-86], [-56], [36], [-66], [18], [-52], [-62], [32], [-4], [-4], [38], [66], [86], [60], [-42], [76], [-78], [64], [66], [-32], [42], [-42], [4], [96], [44], [-36], [46], [-42], [24], [-78], [50], [96], [0], [18], [12], [-36], [-54], [58], [52], [90], [20], [86], [-60], [-44], [84], [-18], [-6], [-78], [-72], [-4], [-10], [60], [-102], [30], [-14], [42], [-48], [30], [-76], [60], [-90], [-98], [-80], [28], [-4], [24], [78], [-54], [80], [-54], [60], [98], [-52], [-90], [-38], [84]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_3136_a_Hecke(Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_3136_2_a_ba();".
// 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_3136_2_a_ba(:prec:=1)
    chi := MakeCharacter_3136_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_3136_2_a_ba();".
// 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_3136_2_a_ba( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_3136_a();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,2,sign)));
    Vf := Kernel([<3,R![-2, 1]>,<5,R![-2, 1]>,<11,R![4, 1]>],Snew);
    return Vf;
end function;