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A108459
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Number of labeled partitions of (n,n) into pairs (i,j).
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5
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1, 1, 5, 52, 855, 19921, 614866, 24040451, 1152972925, 66200911138, 4465023867757, 348383154017581, 31052765897026352, 3128792250765898965, 353179564583216567917, 44320731930172534543092
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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COMMENTS
| Partitions of n black objects labeled 1..n and n white objects labeled 1..n. Each partition must have at least one white object.
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FORMULA
| a(n) = Sum_{k=0..n} k^n*Stirling2(n,k). - Vladeta Jovovic (vladeta(AT)eunet.rs), Aug 31 2006
E.g.f.: Sum_{n>=0} (exp(n*x)-1)^n/n!. - Vladeta Jovovic (vladeta(AT)eunet.rs), Jul 12 2007
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CROSSREFS
| Main diagonal of A108458. Cf. A108461.
Sequence in context: A071583 A099881 A196531 * A076281 A099977 A001173
Adjacent sequences: A108456 A108457 A108458 * A108460 A108461 A108462
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KEYWORD
| nonn
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AUTHOR
| Christian G. Bower (bowerc(AT)usa.net), Jun 03 2005
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