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A002040
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Related to partitions.
(Formerly M1159 N0442)
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2
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1, 2, 4, 8, 21, 52, 131, 316, 765, 1846, 4494, 10944, 26654, 64798, 157502, 382868, 931028, 2264106, 5505777, 13387880, 32553601, 79156974, 192479838, 468039888, 1138098210, 2767421826, 6729311459, 16363118556, 39788886610, 96751470494
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| The subsequence of primes begins 2, 131, 32553601, no more though a(29). [Jonathan Vos Post, Jan 28 2011]
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REFERENCES
| J. M. Gandhi, On numbers related to partitions of a number, Amer. Math. Monthly, 76 (1969), 1033-1036.
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
| Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
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FORMULA
| G.f.: 1/(f(q)') where f(-q)=Product_{k>0} (1-q^k) is one of Ramanujan's theta functions. - Michael Somos, Apr 08 2003
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PROG
| (PARI) a(n)=polcoeff(1/eta(-x+x^2*O(x^n))', n)
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CROSSREFS
| Cf. A002039, A000203.
Sequence in context: A112278 A059731 A001315 * A162110 A108071 A055876
Adjacent sequences: A002037 A002038 A002039 * A002041 A002042 A002043
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KEYWORD
| nonn,easy,nice
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| Formula corrected and sequence extended by Michael Somos
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