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A045992 binomial(2n,n)-n; number of (weakly) increasing or decreasing maps from 1,...,n to 1,...,n. 4
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; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..24.

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 * A217539 A046723 A030529

Adjacent sequences:  A045989 A045990 A045991 * A045993 A045994 A045995

KEYWORD

nonn

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified April 16 02:33 EDT 2014. Contains 240534 sequences.