A054182 Number of positive integers <= 2^n of form 6*x^2 + 7*y^2.

0, 0, 0, 2, 3, 6, 11, 20, 36, 69, 126, 237, 446, 841, 1595, 3046, 5840, 11238, 21684, 41955, 81333, 158007, 307378, 598968, 1168767, 2283307, 4465653, 8742429, 17130723, 33594988, 65933365, 129491817, 254484590, 500430065, 984625784

Offset

0,4

Links

Table of n, a(n) for n=0..34.

Index entries for sequences related to populations of quadratic forms

Prog

(PARI)
is_A020689(n) = { my(r); forstep(y=sqrtint(ceil(n/7)), 0, -1, r = (n-7*(y^2)); if(!(r%6) && issquare(r/6), return(1))); (0); };
A054182(n) = sum(i=1, 2^n, is_A020689(i)); \\ (Very naive and slow) - Antti Karttunen, Jan 04 2025

Crossrefs

Cf. A020689.

Sequence in context: A018076 A010033 A065615 * A358709 A346736 A335628

Adjacent sequences: A054179 A054180 A054181 * A054183 A054184 A054185

Keyword

nonn,more

Author

David W. Wilson

Status

approved