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Search: id:A078509
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| A078509 |
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Number of permutations p of {1,2,...,n} such that p(i)-i != 1 and p(i)-i != 2 for all i. |
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+0
1
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| 1, 1, 1, 5, 23, 131, 883, 6859, 60301, 591605, 6405317, 75843233, 974763571, 13512607303, 200949508327, 3190881283415, 53880906258521, 964039575154409, 18217997734199113, 362584510633666621
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OFFSET
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1,4
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FORMULA
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G.f.: x/(1+x)*Sum_{n>=0} (n+1)!*(x/(1+x)^2)^n. a(n) = Sum_{k=1..n} (-1)^(n-k)*k!*binomial(n+k-2,2*k-2). - Vladeta Jovovic (vladeta(AT)Eunet.yu), Jul 16 2007
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CROSSREFS
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Cf. A000255, A055790, A001883, A001887, A075851, A075852.
Sequence in context: A121636 A020032 A009321 this_sequence A077240 A129098 A047049
Adjacent sequences: A078506 A078507 A078508 this_sequence A078510 A078511 A078512
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KEYWORD
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nonn
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AUTHOR
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Vladimir Baltic, Vladeta Jovovic (vladeta(AT)Eunet.yu), Jan 05 2003
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