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Search: id:A000303
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| A000303 |
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Number of permutations of [n] in which the longest run has length 2.
(Formerly M3522 N1430)
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+0
2
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| 1, 4, 16, 69, 348, 2016, 13357, 99376, 822040, 7477161, 74207208, 797771520, 9236662345, 114579019468, 1516103040832, 21314681315997
(list; graph; listen)
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OFFSET
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2,2
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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. 261, Table 7.4.1.
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EXAMPLE
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a(3)=4 because we have (13)2, 2(13), (23)1, 3(12), where the parentheses surround runs of length 2.
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CROSSREFS
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Column 2 of A008304.
Sequence in context: A151243 A006319 A059606 this_sequence A144316 A133789 A151244
Adjacent sequences: A000300 A000301 A000302 this_sequence A000304 A000305 A000306
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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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Better description from Emeric Deutsch (deutsch(AT)duke.poly.edu), May 08 2004
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