A177475 Number of permutations of order n avoiding the consecutive pattern 131'2.

1, 1, 2, 6, 20, 81, 390, 2161, 13678, 96983, 764368, 6630898, 62748250, 643442919, 7104914398, 84062375725, 1060919238874, 14226075039395, 201982580807466, 3027049675655253, 47753241018325280, 790998083929598213, 13726222157931958274, 249018700470309832015, 4714071198944211367704

Offset

0,3

Comments

To avoid 131'2 means not to have four consecutive letters such that if the third letter is removed, then in the obtained 3 letter word the smallest letter is the first one, and the largest letter is the second one.

Links

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

S. Kitaev, Introduction to partially ordered patterns, Discrete Applied Mathematics 155 (2007), 929-944.

S. Kitaev, Introduction to partially ordered patterns.

Crossrefs

Cf. A117156, A177470, A177471, A177472, A177473, A177476, A177477, A177478, A177479, A177480, A177481, A177482, A177483, A177484, A376694.

Sequence in context: A189839 A117574 A177481 * A118476 A260788 A337274

Adjacent sequences: A177472 A177473 A177474 * A177476 A177477 A177478

Keyword

nonn

Author

Signy Olafsdottir (signy06(AT)ru.is), May 09 2010

Extensions

Edited and terms a(0),a(10)-a(24) added by Max Alekseyev, Oct 02 2024

Status

approved