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Search: id:A099022
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| A099022 |
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Sum[k=0..n, C(n,k) * (2n-k)! ]. |
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+0
4
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| 1, 3, 38, 1158, 65304, 5900520, 780827760, 142358474160, 34209760152960, 10478436416945280, 3984884716852972800, 1842169367191937414400, 1017403495472574045158400, 661599650478455071589606400
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Diagonal of Euler-Seidel matrix with start sequence n!.
Number of ways to use the elements of {1,..,k}, n<=k<=2n, once each to form a sequence of n lists, each having length 1 or 2. - Bob Proctor, Apr 18 2005, Jun 26 2006
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LINKS
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Index entries for related partition-counting sequences
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FORMULA
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T(2n, n), where T is the triangle in A076571.
a(n) = 2*n*(2*n-1)*a(n-1)+n*(n-1)*a(n-2). - Vladeta Jovovic (vladeta(AT)Eunet.yu), Sep 27 2004
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CROSSREFS
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a(n) = n!*A001517(n).
A082765(n) = Sum[C(n, k)*a(k), 0<=k<=n].
Replace "lists" by "sets" in comment: A105749.
Adjacent sequences: A099019 A099020 A099021 this_sequence A099023 A099024 A099025
Sequence in context: A072331 A109518 A062155 this_sequence A136638 A134106 A082954
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KEYWORD
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nonn
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AUTHOR
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Ralf Stephan, Sep 23 2004
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