
// Make newform 112.2.p.b in Magma, downloaded from the LMFDB on 21 December 2025.
// To make the character of type GrpDrchElt, type "MakeCharacter_112_p();"
// To make the character of type GrpDrchElt with Codomain the HeckeField, type "MakeCharacter_112_p_Hecke();"
// To make the coeffs of the qexp of the newform in the Hecke field type "qexpCoeffs();"
// To make the newform (type ModFrm), type "MakeNewformModFrm_112_2_p_b();".
// 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_112_2_p_b();".
// 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
        poly := [1, -1, 1];
        Kf := NumberField(Polynomial([elt : elt in poly]));
        AssignNames(~Kf, ["nu"]);
    end if;
    Rfbasis := [Kf.1^i : i in [0..Degree(Kf)-1]];
    inp_vec := Vector(Rfbasis)*ChangeRing(Transpose(Matrix([[elt : elt in row] : row in input])),Kf);
    return Eltseq(inp_vec);
end function;


// To make the character of type GrpDrchElt, type "MakeCharacter_112_p();"
function MakeCharacter_112_p()
    N := 112;
    order := 6;
    char_gens := [15, 85, 17];
    v := [3, 6, 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;

// To make the character of type GrpDrchElt with Codomain the HeckeField, type "MakeCharacter_112_p_Hecke();"
function MakeCharacter_112_p_Hecke( : Kf := false)
    N := 112;
    order := 6;
    char_gens := [15, 85, 17];
    char_values := [[-1, 0], [1, 0], [0, 1]];
    assert UnitGenerators(DirichletGroup(N)) eq char_gens;
    values := ConvertToHeckeField(char_values : pass_field := ISA(Type(Kf), Fld), Kf := Kf); // the value of chi on the gens as elements in the Hecke field
    F := Universe(values);// the Hecke field
    chi := DirichletCharacterFromValuesOnUnitGenerators(DirichletGroup(N,F),values);
    return chi;
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], [1, -1], [2, -1], [-1, -2], [1, 1], [0, 0], [-3, -3], [0, 7], [-10, 5], [-6, 0], [5, -5], [0, 5], [4, -8], [2, -4], [0, 3], [9, -9], [9, -9], [10, -5], [-3, -3], [-2, 4], [1, 1], [6, -3], [-12, 0], [-14, 7], [4, -8], [-3, -3], [0, -1], [6, -3], [-11, 11], [6, 0], [-2, 4], [0, -21], [-3, 3], [4, 0], [0, 9], [-7, -7], [9, 9], [14, -7], [-12, 0], [10, -5], [9, 9], [-4, 8], [14, -7], [5, -5], [-6, 0], [-11, 11], [-14, 28], [-16, 0], [21, -21], [-14, 7], [0, -3], [-6, 12], [-7, -7], [0, 0], [-22, 11], [5, 5], [1, 1], [0, -1], [17, -17], [6, 0], [-11, 11], [-12, 24], [20, 0], [33, -33], [34, -17], [0, 21], [-34, 17], [14, 0], [5, 5], [16, -32], [-11, -11], [-18, 9], [1, -1], [0, 13], [6, -12], [0, 27], [21, -21], [-14, 7], [0, -3], [-3, -3], [-12, 0], [10, 0], [17, 17], [-20, 40], [0, 19], [-26, 13], [-18, 0], [0, 1], [16, -32], [-2, 4], [0, 3], [9, -9], [5, 5], [-10, 20], [14, -7], [-24, 0], [18, -9], [17, 17], [0, 23], [0, -7], [14, -28], [-3, 3], [-15, 15], [0, -39], [-7, -7], [9, 9], [12, 0], [-22, 11], [-19, -19], [-4, 8], [0, -29], [-11, 11], [-18, 0], [-7, 7], [-26, 52], [9, -9], [-4, 0], [-15, 15], [0, -3], [-14, 28], [-23, -23], [-50, 0], [-46, 23], [25, 25], [0, -13], [30, 0], [0, -35], [0, -33], [-32, 0], [-22, 11], [1, 1], [22, -44], [46, -23], [26, 0], [-6, 3], [-4, 8], [5, 5], [-7, 7], [8, -16], [-15, 15], [4, 0], [0, 57], [13, 13], [-22, 44], [5, 5], [0, 0], [-8, 16], [25, 25], [0, -41], [54, -27], [0, -47], [-8, 16], [26, -52], [0, 3], [-3, -3], [6, -12], [-50, 25], [-30, 15], [24, -48], [17, 17], [-34, 17], [-18, 0], [-18, 36], [0, 3], [-27, 27], [-3, 3], [-3, -3], [1, 1]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_112_p_Hecke( : Kf := Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_112_2_p_b();".
// 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_112_2_p_b(:prec:=2)
    chi := MakeCharacter_112_p();
    f_vec := qexpCoeffs();
    Kf := Universe(f_vec);
    // SetVerbose("ModularForms", true);
    // SetVerbose("ModularSymbols", true);
    S := CuspidalSubspace(ModularForms(chi, 2));
    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_112_2_p_b();".
// 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_112_2_p_b( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_112_p();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,2,sign)));
    Vf := Kernel([<3,R![1, -1, 1]>],Snew);
    return Vf;
end function;