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A001344
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Sum(k=0..2, (n+k)! * C(2,k)).
(Formerly M1405 N0548)
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1
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2, 5, 11, 38, 174, 984, 6600, 51120, 448560, 4394880, 47537280, 562464000, 7224940800, 100111334400, 1488257971200, 23625316915200, 398840682240000, 7134671351808000
(list; graph; refs; listen; history; internal format)
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OFFSET
| -1,1
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COMMENTS
| if we discard the first two terms and set a(0)= 11 then a(n) = (n+1)!*(n^2+7*n+11). [From Gary Detlefs (gdetlefs(AT)aol.com), Aug 11 2010]
For nonnegative n, a(n) equals the permanent of the (n+2) X (n+2) matrix with a 2 in the upper right corner, a 2 in the lower left corner, and 1's everywhere else. [From John M. Campbell (jmaxwellcampbell(AT)gmail.com), May 25, 2011]
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REFERENCES
| Biondi, E.; Divieti, L.; Guardabassi, G.; Counting paths, circuits, chains and cycles in graphs: A unified approach. Canad. J. Math. 22 1970 22-35.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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CROSSREFS
| Sequence in context: A131581 A195985 A056301 * A056302 A065850 A191029
Adjacent sequences: A001341 A001342 A001343 * A001345 A001346 A001347
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KEYWORD
| nonn,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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