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A165544
Number of permutations of length n which avoid the patterns 4123 and 3412.
0
1, 1, 2, 6, 22, 89, 381, 1696, 7781, 36572, 175277, 853410, 4209376, 20988122, 105611537, 535638107
OFFSET
0,3
LINKS
Darla Kremer and Wai Chee Shiu, Finite transition matrices for permutations avoiding pairs of length four patterns, Discrete Math. 268 (2003), 171-183. MR1983276 (2004b:05006). See Table 1.
EXAMPLE
There are 22 permutations of length 4 which avoid these two patterns, so a(4)=22.
CROSSREFS
Sequence in context: A165543 A049123 A200753 * A150268 A369439 A165545
KEYWORD
nonn,more
AUTHOR
Vincent Vatter, Sep 21 2009
EXTENSIONS
The 6th term should be 381, not 3381. Sorry about that. - Vincent Vatter, Oct 01 2010
a(0)=1 prepended by Alois P. Heinz, Dec 09 2015
a(13)-a(15) from Lars Blomberg, Apr 26 2018
STATUS
approved