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Search: id:A099745
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A099745 Number of permutations of [n] with exactly 2 valleys which avoid the permutation 1324. +0
1
0, 0, 0, 0, 12, 168, 1409, 9187, 51362, 258674, 1207855, 5326205, 22459080, 91368900, 360977373, 1391835607, 5257593566, 19515948358, 71358739003, 257521313441, 918732810340, 3244576312440, 11355547678665, 39423281302875 (list; graph; listen)
OFFSET

1,5
FORMULA

G.f.: x^5*(12-72*x+137*x^2-81*x^3)/((1-3*x)^4*(1-2*x)^4).

CROSSREFS

Cf. A000079.

Sequence in context: A046174 A055760 A056591 this_sequence A079679 A113380 A071103

Adjacent sequences: A099742 A099743 A099744 this_sequence A099746 A099747 A099748

KEYWORD

nonn

AUTHOR

Mike Zabrocki (zabrocki(AT)mathstat.yorku.ca), Nov 09 2004

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Last modified November 27 22:38 EST 2009. Contains 167602 sequences.

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