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Search: id:A000024
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| A000024 |
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Number of positive integers <= 2^n of form x^2 + 10 y^2.
(Formerly M0368 N0139)
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+0
1
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| 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
(list; graph; listen)
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OFFSET
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0,3
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
D. Shanks and L. P. Schmid, Variations on a theorem of Landau. Part I, Math. Comp., 20 (1966), 551-569.
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LINKS
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Index entries for sequences related to populations of quadratic forms
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PROGRAM
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(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))
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CROSSREFS
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Adjacent sequences: A000021 A000022 A000023 this_sequence A000025 A000026 A000027
Sequence in context: A101372 A133374 A054226 this_sequence A005223 A118680 A094116
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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