A045992 - OEIS

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A045992

binomial(2n,n)-n; number of (weakly) increasing or decreasing maps from 1,...,n to 1,...,n.

1, 1, 4, 17, 66, 247, 918, 3425, 12862, 48611, 184746, 705421, 2704144, 10400587, 40116586, 155117505, 601080374, 2333606203, 9075135282, 35345263781, 137846528800, 538257874419, 2104098963698, 8233430727577, 32247603683076 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,3`
	EXAMPLE	`a(3)=17 since can map (1,2,3) to (1,1,1), (1,1,2), (1,1,3), (1,2,2), (1,2,3), (1,3,3), (2,1,1), (2,2,1), (2,2,2), (2,2,3), (2,3,3), (3,1,1), (3,2,1), (3,2,2), (3,3,1), (3,3,2), or (3,3,3) but not for example to (1,3,2)`
	CROSSREFS	`Cf. A000312, A000984, A001700.` `Sequence in context: A181410 A102207 A202555 * A046723 A030529 A081113` `Adjacent sequences: A045989 A045990 A045991 * A045993 A045994 A045995`
	KEYWORD	`nonn`
	AUTHOR	`N. J. A. Sloane (njas(AT)research.att.com).`

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Last modified February 16 07:39 EST 2012. Contains 205881 sequences.