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Search: id:A045992
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A045992 binomial(2n,n)-n; number of (weakly) increasing or decreasing maps from 1,...,n to 1,...,n. +0
3
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; listen)
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: A005784 A095252 A102207 this_sequence A046723 A030529 A081113

Adjacent sequences: A045989 A045990 A045991 this_sequence A045993 A045994 A045995

KEYWORD

nonn

AUTHOR

njas

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Last modified July 26 13:41 EDT 2008. Contains 142293 sequences.


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