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Search: id:A006505
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| A006505 |
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Number of partitions of an n-set into boxes of size >2.
(Formerly M4789)
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+0
4
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| 1, 0, 0, 1, 1, 1, 11, 36, 92, 491, 2557, 11353, 60105, 362506, 2169246, 13580815, 91927435, 650078097, 4762023647, 36508923530, 292117087090, 2424048335917, 20847410586719, 185754044235873, 1711253808769653, 16272637428430152
(list; graph; listen)
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OFFSET
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0,7
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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).
E. A. Enneking and J. C. Ahuja, Generalized Bell numbers, Fib. Quart., 14 (1976), 67-73.
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 102
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FORMULA
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Expansion of exp ( exp x - 1 - x - (1/2)*x^2 ).
a(n)=sum_{k=1..[n/3]} A059022(n,k), n>=3. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 08 2008]
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MAPLE
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Copy ZL := [ B, {B=Set(Set(Z, card>=3))}, labeled ]: [seq(combstruct[count](ZL, size=n), n=0..25)]; - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 13 2007
G:={P=Set(Set(Atom, card>=3))}:combstruct[gfsolve](G, unlabeled, x):seq(combstruct[count]([P, G, labeled], size=i), i=0..25); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Dec 16 2007
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CROSSREFS
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Cf. A000110, A000296, A057814, A057837.
Sequence in context: A081438 A160483 A034309 this_sequence A005000 A004637 A052526
Adjacent sequences: A006502 A006503 A006504 this_sequence A006506 A006507 A006508
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KEYWORD
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nonn,easy
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
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More terms from Christian G. Bower (bowerc(AT)usa.net), Nov 09 2000
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