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A086853
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Number of permutations of length n with exactly 2 rising or falling successions.
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7
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0, 0, 0, 2, 10, 48, 256, 1670, 12846, 112820, 1108612, 12032154, 142852450, 1840969784, 25587270600, 381460235918, 6071318154166, 102742200205980, 1841978156709676, 34874169034136930, 695294184953602602, 14560120360421802464, 319510983674891800240
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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COMMENTS
| Permutations of 12...n such that exactly 2 of the following occur: 12, 23, ..., (n-1)n, 21, 32, ..., n(n-1).
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REFERENCES
| 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
| Coefficient of t^2 in S[n](t) defined in A002464.
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CROSSREFS
| Cf. A002464, A000130, A000349, A001267, A086852, A086854. A diagonal of A001100.
Sequence in context: A065982 A114693 A121950 * A036918 A200540 A166922
Adjacent sequences: A086850 A086851 A086852 * A086854 A086855 A086856
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Aug 19 2003
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