A248900 Number of permutations of [n] avoiding patterns 2431 and 54321.

1, 1, 2, 6, 23, 102, 492, 2492, 13003, 69172, 372963, 2031174, 11148948, 61588814, 342068774, 1908740089, 10694374242, 60137305751, 339276548456, 1919787554118, 10892575241125, 61957028188350, 353224194632459, 2018076850631391, 11552829351121139, 66259093178740462

Offset: 0

Author

Nathaniel Shar, Mar 06 2015

Keywords

• nonn

Examples

			a(4) = 23 because all permutations of length 4 except 2431 lie in this set.
		

Links

• Nathaniel Shar, Table of n, a(n) for n = 0..80
• Nathaniel Shar, Maple code

Crossrefs

Cf. A022558, A047889.