A027616 - OEIS

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A027616

Number of permutations of n elements containing a 2-cycle.

0, 0, 1, 3, 9, 45, 285, 1995, 15855, 142695, 1427895, 15706845, 188471745, 2450132685, 34301992725, 514529890875 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,4`
	FORMULA	`n! * { 1 - sum[ k=0..floor(n/2) ] (-1)^k / (2^k * k!) }.` `a(n) + A000266(n) = n!. - Yuval Dekel (dekelyuval(AT)hotmail.com), Nov 09 2003`
	CROSSREFS	`Sequence in context: A038059 A174318 A004990 * A013492 A106341 A065407` `Adjacent sequences: A027613 A027614 A027615 * A027617 A027618 A027619`
	KEYWORD	`nonn`
	AUTHOR	`Joe Keane (jgk(AT)jgk.org)`

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Last modified February 16 06:27 EST 2012. Contains 205860 sequences.