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Search: id:A001266
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| A001266 |
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One-half the number of permutations of length n without rising or falling successions.
(Formerly M4426 N1871)
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+0
5
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| 0, 0, 1, 7, 45, 323, 2621, 23811, 239653, 2648395, 31889517, 415641779, 5830753109, 87601592187, 1403439027805, 23883728565283, 430284458893701, 8181419271349931, 163730286973255373, 3440164703027845395, 75718273707281368117, 1742211593431076483419
(list; graph; listen)
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OFFSET
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2,4
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COMMENT
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(1/2) times number of permutations of 12...n such that none of the following occur: 12, 23, ..., (n-1)n, 21, 32, ..., n(n-1).
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
F. N. David, M. G. Kendall and D. E. Barton, Symmetric Function and Allied Tables, Cambridge, 1966, p. 263.
J. Riordan, A recurrence for permutations without rising or falling successions. Ann. Math. Statist. 36 (1965), 708-710.
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FORMULA
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(1/2) times coefficient of t^0 in S[n](t) defined in A002464.
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CROSSREFS
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Sequence A002464 divided by 2 for n >= 2. A diagonal of A010028.
Adjacent sequences: A001263 A001264 A001265 this_sequence A001267 A001268 A001269
Sequence in context: A103719 A134437 A018927 this_sequence A071971 A006680 A034471
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
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More terms from Barbara Haas Margolius (margolius(AT)math.csuohio.edu) 2/16/01
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