

A189282


Number of permutations p of 1,2,...,n satisfying p(i+3)p(i)<>3 for all 1<=i<=n3.


5



1, 1, 2, 6, 22, 98, 534, 3414, 25498, 217338, 2080990, 22076030, 256888218, 3252308706, 44497313158, 654139144158, 10281397705242, 172033123244330, 3052895403376110, 57266799403366334, 1132124282036449570, 23524895818926592242
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OFFSET

0,3


COMMENTS

a(n) is also number of ways to place n nonattacking pieces rook + semileaper[3,3] on an n X n chessboard.


LINKS

Christoph Koutschan, Table of n, a(n) for n = 0..48 (terms 0..30 from Vaclav Kotesovec, terms 31..36 from Manuel Kauers and Christoph Koutschan, terms 37..48 from George Spahn and Doron Zeilberger)


FORMULA

Asymptotics: a(n)/n! ~ (1 + 5/n + 6/n^2)/e.


CROSSREFS



KEYWORD

nonn,hard


AUTHOR



STATUS

approved



