A107502 Theta series of quadratic form with Gram matrix [ 4, 1, 0, -1; 1, 10, 0, 3; 0, 0, 26, 13; -1, 3, 13, 36].

1, 0, 2, 0, 0, 2, 2, 0, 4, 0, 0, 2, 0, 2, 0, 6, 0, 0, 10, 8, 14, 12, 0, 0, 20, 0, 6, 0, 16, 0, 0, 8, 18, 18, 12, 0, 0, 12, 0, 8, 0, 6, 0, 0, 30, 22, 20, 10, 0, 0, 22, 0, 14, 0, 38, 0, 0, 22, 30, 18, 48, 0, 0, 30, 0, 12, 0, 22, 0, 0, 38, 16, 50, 30, 0, 0, 46, 0

Offset

0,3

Comments

G.f. is theta_6 in the Parry 1979 reference on page 166. This theta series is an element of the space of modular forms on Gamma_0(169) of weight 2 and dimension 21. - Andy Huchala, May 13 2023

Links

Andy Huchala, Table of n, a(n) for n = 0..20000

W. R. Parry, A negative result on the representation of modular forms by theta series, J. Reine Angew. Math., 310 (1979), 151-170.

Example

G.f. = 1 + 2*q^4 + 2*q^10 + 2*q^12 + ...

Prog

(Magma)
prec := 90;
ls := [[4, 1, 0, -1], [1, 10, 0, 3], [0, 0, 26, 13], [-1, 3, 13, 36]];
S := Matrix(ls);
L := LatticeWithGram(S);
M := ThetaSeriesModularFormSpace(L);
B := Basis(M, prec);
T<q> := ThetaSeries(L, 48);
coeffs := [Coefficients(T)[2*i-1] : i in [1..23]];
Coefficients(&+[coeffs[i]*B[i] :i in [1..13]]+&+[coeffs[i+1]*B[i] :i in [14..19]] + coeffs[22]*B[20] + coeffs[23]*B[21]); // Andy Huchala, May 13 2023

Crossrefs

Cf. A107498, A107499, A107500, A107501, A107503, A107504, A107505.

Sequence in context: A284059 A329767 A356018 * A230419 A146165 A308831

Adjacent sequences: A107499 A107500 A107501 * A107503 A107504 A107505

Keyword

nonn

Author

N. J. A. Sloane, May 28 2005

Extensions

Name clarified and more terms from Andy Huchala, May 13 2023

Status

approved