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A000690
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Landau's approximation to population of x^2 + y^2.
(Formerly M0586 N0212)
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2
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1, 2, 3, 4, 7, 13, 24, 44, 83, 157, 297, 567, 1085, 2086, 4019, 7766, 15039, 29181, 56717, 110408, 215225, 420076, 820836, 1605587, 3143562, 6160098, 12080946, 23710229, 46565965, 91512121, 179947985, 354043613, 696935548, 1372589372
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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REFERENCES
| D. Shanks, The second-order term in the asymptotic expansion of B(x), Math. Comp., 18 (1964), 75-86.
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).
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LINKS
| Index entries for sequences related to populations of quadratic forms
Sean A. Irvine, Table of n, a(n) for n = 0..999
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FORMULA
| a(n) = round(b*2^n/sqrt(ln(2^n))) where b=0.764223654... is the Landau-Ramanujan constant (A064533).
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CROSSREFS
| A064533
Sequence in context: A096723 A137495 A099779 * A049876 A049795 A014251
Adjacent sequences: A000687 A000688 A000689 * A000691 A000692 A000693
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms from Sean A. Irvine (sairvin(AT)xtra.co.nz), Feb 23 2011
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