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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 (list; graph; refs; listen; history; text; internal format)
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 3412-patterns 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.: (1-4*x+x^3)/((1-x) * (1-4*x-x^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 3412-patterns.  (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

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Last modified March 31 03:48 EDT 2020. Contains 333136 sequences. (Running on oeis4.)