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A001925
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From rook polynomials.
(Formerly M4151 N1724)
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3
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1, 6, 22, 64, 162, 374, 809, 1668, 3316, 6408, 12108, 22468, 41081, 74202, 132666, 235160, 413790, 723530, 1258225, 2177640, 3753096, 6444336, 11028792, 18818664, 32024977, 54367374, 92094334, 155688208, 262711866, 442556798
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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REFERENCES
| J. Riordan, Discordant permutations, Scripta Math., 20 (1954), 14-23.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
| S. Plouffe, Approximations de S\'{e}ries G\'{e}n\'{e}ratrices et Quelques Conjectures, Dissertation, Universit\'{e} du Qu\'{e}bec \`{a} Montr\'{e}al, 1992.
S. Plouffe, 1031 Generating Functions and Conjectures, Universit\'{e} du Qu\'{e}bec \`{a} Montr\'{e}al, 1992.
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FORMULA
| Riordan gives the g.f. (1+x)/[(1-x-x^2)^2*(1-x)^3].
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MAPLE
| A001925:=-(1+z)/(z**2+z-1)**2/(z-1)**3; [Conjectured by S. Plouffe in his 1992 dissertation.]
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CROSSREFS
| Cf. A002940.
Sequence in context: A120477 A053739 A055797 * A002663 A099855 A003469
Adjacent sequences: A001922 A001923 A001924 * A001926 A001927 A001928
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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