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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 >= 2, 0<=k<=n-2).
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3
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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, 242094, 32028, 4414, 640, 98, 16, 2, 1, 37054436, 2510733, 306723, 38893, 5164, 724, 107, 17, 2, 1
(list; table; graph; refs; listen; history; internal format)
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OFFSET
| 2,1
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LINKS
| J. Riordan, Permutations without 3-sequences, Bull. Amer. Math. Soc., 51 (1945), 745-748.
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FORMULA
| Riordan gives a recurrence.
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EXAMPLE
| 2; 5 1; 21 2 1; 106 11 2 1; ...
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CROSSREFS
| Columns give A002628, A002629, A002630.
Sequence in context: A187244 A120294 A186766 * A177250 A102786 A190950
Adjacent sequences: A047918 A047919 A047920 * A047922 A047923 A047924
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KEYWORD
| nonn,tabl,nice,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| Edited and extended by Max Alekseyev (maxale(AT)gmail.com), Sep 05 2010
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