

A257562


Number of permutations of length n that avoid the patterns 4123, 4231, and 4312.


4



1, 1, 2, 6, 21, 79, 310, 1251, 5150, 21517, 90921, 387595, 1663936, 7183750, 31158310, 135661904, 592558096, 2595232344, 11392504426, 50109205789, 220777103354, 974162444028, 4303957562319, 19036842605855, 84285643628790, 373502845338552, 1656428550764640, 7351106011540209, 32643855249507805, 145040974005303590, 644756480385363800
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OFFSET

0,3


COMMENTS

G.f. conjectured to be nonDfinite (see Albert et al. link). Jay Pantone, Oct 01 2015
Unlike A061552, whose g.f. is also conjectured to be nonDfinite, thousands of terms of the counting sequence are known.  David Callan, Aug 29 2017


LINKS



EXAMPLE

a(4) = 21 because there are 24 permutations of length 4 and 3 of them do not avoid 4123, 4231, and 4312.


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



