
// Make newform 1710.2.a.i in Magma, downloaded from the LMFDB on 23 April 2024.
// To make the character of type GrpDrchElt, type "MakeCharacter_1710_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_1710_2_a_i();".
// 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_1710_2_a_i();".
// 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_1710_a();"
function MakeCharacter_1710_a()
    N := 1710;
    order := 1;
    char_gens := [191, 1027, 1351];
    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_1710_a_Hecke(Kf)
    return MakeCharacter_1710_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 := [[-1], [0], [1], [0], [-4], [2], [-2], [-1], [-4], [-6], [4], [-6], [-10], [-4], [12], [-6], [12], [-2], [4], [-8], [-6], [-4], [12], [-10], [2], [-10], [-4], [4], [-6], [14], [-4], [12], [-10], [-20], [-18], [-12], [-2], [-4], [0], [10], [-20], [18], [-20], [2], [-2], [0], [-4], [12], [20], [-10], [-18], [-12], [26], [20], [-2], [4], [2], [8], [-2], [6], [-28], [2], [4], [28], [-6], [26], [28], [26], [12], [-10], [-26], [-12], [24], [-22], [-20], [0], [22], [-18], [14], [18], [-12], [26], [-8], [34], [12], [-4], [30], [-6], [38], [8], [28], [-20], [-20], [36], [-36], [36], [18], [6], [28], [-10], [20], [-42], [-4], [38], [-44], [-30], [28], [-10], [-16], [-38], [4], [22], [14], [4], [-8], [-18], [-4], [-36], [6], [12], [10], [-14], [42], [-36], [-4], [-18], [-10], [-28], [40], [46], [52], [-16], [-4], [38], [-18], [-46], [-30], [-52], [-54], [-34], [-20], [22], [8], [-36], [10], [0], [14], [-26], [36], [-8], [-46], [30], [20], [48], [28], [-24], [8], [6], [10], [-30], [-52], [-42], [-32], [36], [-2], [-56], [4], [38], [-6], [-34], [-44], [-54], [12], [-22], [60], [-10], [12], [62], [-28], [62], [24], [-28], [-14], [6], [12], [-2], [58], [-20], [-14], [-52], [42], [-44], [-44], [-6], [-60], [54], [-30], [-50], [-42], [60], [42], [12], [26], [-14], [-4], [-2], [-16], [36], [54], [52], [-62], [70], [16], [-12], [-64], [18], [32], [-50], [-64], [14], [50], [28], [14], [48], [60], [54], [-26], [-24], [-36], [12], [-66], [60], [60], [-58], [-76], [-12], [34], [-42], [36], [8], [44], [-28], [-56], [-38], [14], [12], [64], [20], [-12], [36], [62], [-18], [36], [-70], [6], [-76], [-58], [12], [-38], [-6], [-68], [60], [30], [-6], [-82], [44], [-54], [-10], [-28], [-74], [42], [28], [10], [-56], [-70], [-40], [36], [-38], [-22], [-12], [16], [16], [20], [2], [52], [-20], [-30], [-78], [-16], [-66], [-58], [-52], [54], [20], [-6], [-18], [-20], [-18], [-20], [-52], [-6], [-46], [-16], [-20], [-28], [50], [76], [26], [-4], [-34], [-12], [-18], [-18], [44], [4], [-54], [44], [48], [18], [-2], [-92], [-54], [74], [12], [22], [-38], [-60], [-44], [0], [-50], [-42], [2], [0], [-76], [-20], [-12], [82], [-66], [26], [-32], [58], [38], [82], [-68], [-14], [-20], [62], [-36], [-40], [54], [4], [-86], [38], [-4], [-22], [-42], [-60], [-28], [-18], [-8], [38], [-58], [72], [-44], [84], [-62], [30], [4], [50], [12], [-12], [68], [-46], [-80], [38], [60], [-100], [-46], [-42], [58], [-6], [-10], [-32], [6], [44], [-16], [0], [62], [12], [88], [18], [90], [-60], [44], [24], [-6], [-44], [6], [-4], [-58], [90], [14], [-4], [-90], [-6], [56], [-26], [-18], [28], [-84], [26], [6], [4], [-44], [74], [78], [40], [-68], [-98], [0], [90], [-38], [28], [-44], [42], [42], [-4], [-74], [-4], [-60]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_1710_a_Hecke(Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_1710_2_a_i();".
// 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_1710_2_a_i(:prec:=1)
    chi := MakeCharacter_1710_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_1710_2_a_i();".
// 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_1710_2_a_i( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_1710_a();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,2,sign)));
    Vf := Kernel([<7,R![0, 1]>,<11,R![4, 1]>,<13,R![-2, 1]>,<53,R![6, 1]>],Snew);
    return Vf;
end function;