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Search: id:A000434
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| A000434 |
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Number of permutations of [n] in which the longest run has length 4.
(Formerly M4556 N1938)
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+0
2
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| 1, 8, 67, 602, 5811, 60875, 690729, 8457285, 111323149, 1569068565, 23592426102, 377105857043, 6387313185590, 114303481217895, 2155348564851616
(list; graph; listen)
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OFFSET
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4,2
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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.
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EXAMPLE
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a(5)=8 because we have (1235)4, (1245)3, (1345)2, (2345)1, 5(1234), 4(1235), 3(1245) and 2(1345), where the parentheses surround runs of length 4.
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CROSSREFS
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Cf. A008304.
Sequence in context: A091645 A015574 A152055 this_sequence A050841 A163307 A152105
Adjacent sequences: A000431 A000432 A000433 this_sequence A000435 A000436 A000437
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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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