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Search: id:A006198
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| A006198 |
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Number of partitions into pairs.
(Formerly M4241)
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+0
2
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| 1, 1, 6, 41, 365, 3984, 51499, 769159, 13031514, 246925295, 5173842311, 118776068256, 2964697094281, 79937923931761, 2315462770608870, 71705109685449689
(list; graph; listen)
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OFFSET
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1,3
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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).
G. Kreweras and Y. Poupard, Sur les partitions en paires d'un ensemble fini totalement ordonne, Publications de l'Institut de Statistique de l'Universit\'{e} de Paris, 23 (1978), 57-74.
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FORMULA
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a(n) = |A000806(n-1)|+|A000806(n)|. G.f.: Sum_{n>=0} A001147(n)*(x/(1+x)^2)^n. - Vladeta Jovovic (vladeta(AT)eunet.rs), Jun 27 2007
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CROSSREFS
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Sequence in context: A005011 A009122 A094869 this_sequence A167588 A113573 A007130
Adjacent sequences: A006195 A006196 A006197 this_sequence A006199 A006200 A006201
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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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