A000024 Number of positive integers <= 2^n of form x^2 + 10 y^2. (Formerly M0368 N0139)

1, 1, 2, 2, 7, 10, 20, 36, 65, 118, 221, 409, 776, 1463, 2788, 5328, 10222, 19714, 38054, 73685, 142944, 277838, 540889, 1054535, 2058537, 4023278, 7871313, 15414638, 30213190, 59266422, 116343776, 228545682, 449240740, 883570480, 1738769611, 3423469891, 6743730746

Offset

0,3

References

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

Table of n, a(n) for n=0..36.

D. Shanks and L. P. Schmid, Variations on a theorem of Landau. Part I, Math. Comp., 20 (1966), 551-569.

Index entries for sequences related to populations of quadratic forms

Prog

(PARI) a(n)=local(A); if(n<0, 0, A=qfrep([1, 0; 0, 10], 2^n); sum(k=1, 2^n, A[k]!=0))

Crossrefs

Sequence in context: A133374 A267446 A054226 * A005223 A118680 A278457

Adjacent sequences: A000021 A000022 A000023 * A000025 A000026 A000027

Keyword

nonn

Author

N. J. A. Sloane

Status

approved