A029571 - OEIS

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A029571

Number of permutations of an n-set containing a 4-cycle.

0, 0, 0, 0, 6, 30, 180, 1260, 8820, 79380, 793800, 8731800, 106029000, 1378377000, 19297278000, 289459170000, 4627941318000, 78675002406000, 1416150043308000, 26906850822852000, 538156815464268000 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,5`
	FORMULA	`a(n) = n! (1 - sum_{k=0}^Floor[ n/4 ] (-1)^k/(k!4^k)); a(n)/n! is asymptotic to 1-e^(-1/4).`
	CROSSREFS	`Sequence in context: A057754 A001473 A063888 * A109501 A147517 A005922` `Adjacent sequences: A029568 A029569 A029570 * A029572 A029573 A029574`
	KEYWORD	`nonn`
	AUTHOR	`Robert W. Pratt (Rob.Pratt(AT)sas.com)`

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Last modified February 16 09:50 EST 2012. Contains 205904 sequences.