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Search: id:A047921
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| A047921 |
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Triangle of numbers a(n,k) = number of permutations on n letters containing k 3-sequences (n >= 1, 0<=k<=n-2). |
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+0
4
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| 1, 2, 5, 1, 21, 2, 1, 106, 11, 2, 1, 643, 62, 12, 2, 1, 4547, 406, 71, 13, 2, 1, 36696, 3046, 481, 80, 14, 2, 1, 332769, 25737, 3708, 559, 89, 15, 2, 1, 3349507
(list; table; graph; listen)
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OFFSET
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0,2
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REFERENCES
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J. Riordan, Permutations without 3-sequences, Bull. Amer. Math. Soc., 51 (1945), 745-748.
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FORMULA
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Reference gives a recurrence.
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EXAMPLE
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1; 2; 5 1; 21 2 1; 106 11 2 1; ...
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CROSSREFS
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Columns give A002628, A002629, A002630.
Sequence in context: A106852 A162975 A120294 this_sequence A102786 A159985 A146103
Adjacent sequences: A047918 A047919 A047920 this_sequence A047922 A047923 A047924
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KEYWORD
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nonn,tabl,nice,easy,more
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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