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Search: id:A002628
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| A002628 |
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Number of permutations of length n without 3-sequences.
(Formerly M1536 N0600)
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+0
6
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| 1, 2, 5, 21, 106, 643, 4547, 36696, 332769, 3349507, 37054436, 446867351, 5834728509, 82003113550, 1234297698757, 19809901558841, 337707109446702, 6094059760690035, 116052543892621951, 2325905946434516516
(list; graph; listen)
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OFFSET
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1,2
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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).
Jackson, D. M.; Reilly, J. W. Permutations with a prescribed number of p-runs. Ars Combinatoria 1 (1976), number 1, 297-305.
J. Riordan, Permutations without 3-sequences, Bull. Amer. Math. Soc., 51 (1945), 745-748.
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LINKS
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Jackson, D. M. and Read, R. C., A note on permutations without runs of given length, Aequationes Math. 17 (1978), number 2-3, 336-343.
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MAPLE
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seq(coeff(convert(series(add(m!*((t-t^3)/(1-t^3))^m, m=0..50), t, 50), polynom), t, n), n=1..25); (Pab Ter)
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CROSSREFS
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Cf. A047921.
Cf. A165960, A165961, A165962. [From Isaac E. Lambert (lamberti09(AT)mail.wlu.edu), Oct 07 2009]
Sequence in context: A008981 A008982 A130471 this_sequence A020129 A129582 A152576
Adjacent sequences: A002625 A002626 A002627 this_sequence A002629 A002630 A002631
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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 Pab Ter (pabrlos2(AT)yahoo.com), Nov 06 2005
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