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A177475
Number of permutations of order n avoiding the consecutive pattern 131'2.
7
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
S. Kitaev, Introduction to partially ordered patterns, Discrete Applied Mathematics 155 (2007), 929-944.
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