

A191721


Permutations in S_n avoiding the patterns {4321, 34512, 45123, 35412, 43512, 45132, 45213, 53412, 45312, 45231}


0



1, 2, 6, 23, 94, 391, 1633, 6827, 28548, 119384, 499255, 2087854, 8731285, 36513737, 152698377, 638575958, 2670488470, 11167831459, 46703238346, 195310296371, 816776592369, 3415713427499, 14284320005992, 59736216859096
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OFFSET

1,2


COMMENTS

A(n) is also the number of w in S_n for which the number of repeated letters in a reduced decomposition of w equals the number of 321 and 3412patterns in w.
The generating function can be automatically computed by the Maple package INSENC listed in the links.  Vincent Vatter, Jun 16 2011


LINKS

Table of n, a(n) for n=1..24.
B. E. Tenner, Repetition in reduced decompositions, arXiv:1106.2839 [math.CO]
V. Vatter, Maple package INSENC


FORMULA

G.f.: (14*x+x^3)/((1x) * (14*xx^2+x^3)).  Vincent Vatter, Jun 16 2011


EXAMPLE

A(4)=23 because all permutations in S_4 except 4321 avoid these patterns. Also, all permutations in S_4 except 4321 have repeated letters equaling the number of 321 and 3412patterns. (Note that 4321 has 3 repeated letters, but 4 of these patterns.)


CROSSREFS

Sequence in context: A150290 A150291 A150292 * A150293 A150294 A150295
Adjacent sequences: A191718 A191719 A191720 * A191722 A191723 A191724


KEYWORD

nonn


AUTHOR

Bridget Tenner, Jun 13 2011


STATUS

approved



