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

Author

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

Keywords

• nonn

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

• 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.

Extensions

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