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Search: id:A001887
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| A001887 |
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Hit polynomials.
(Formerly M3970 N1640)
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+0
3
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| 1, 0, 0, 0, 1, 5, 33, 236, 1918, 17440, 175649, 1942171, 23396353, 305055960, 4280721564, 64330087888, 1030831875953, 17545848553729, 316150872317105, 6012076099604308, 120330082937778554
(list; graph; listen)
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OFFSET
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0,6
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COMMENT
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Number of permutations p of {1,2,...,n} such that p(i)-i<0 or p(i)-i>2 for all i. - Vladimir Baltic and Vladeta Jovovic (vladeta(AT)Eunet.yu), Jan 05 2003
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REFERENCES
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J. Riordan, ``The enumeration of permutations with three-ply staircase restrictions,'' unpublished memorandum, Bell Telephone Laboratories, Murray Hill, NJ, Oct 1963.
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FORMULA
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G.f.: 1/(x^2-1)*(x-Sum_{n>=0} n!*(x*(x-1)/(x^3-2*x-1))^n). - Vladeta Jovovic (vladeta(AT)Eunet.yu), Jun 30 2007
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CROSSREFS
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Cf. A000255, A000271, A001883, A075851, A075852.
First column of A080061.
Sequence in context: A015544 A083076 A128418 this_sequence A118803 A093427 A084131
Adjacent sequences: A001884 A001885 A001886 this_sequence A001888 A001889 A001890
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KEYWORD
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nonn
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AUTHOR
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njas
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EXTENSIONS
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More terms from Vladimir Baltic and Vladeta Jovovic (vladeta(AT)Eunet.yu), Jan 05 2003
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