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A116770
Number of permutations of length n which avoid the patterns 1243, 1342, 4312.
0
1, 2, 6, 21, 73, 234, 691, 1910, 5019, 12690, 31147, 74694, 175843, 407810, 934179, 2117958, 4759915, 10617234, 23527867, 51839462, 113639955, 247988802, 538968691, 1167065766, 2518680283, 5419041554, 11626611531, 24880612230
OFFSET
1,2
FORMULA
G.f.: A(x) = {x(3x^6-12x^5+22x^4-30x^3+21x^2-7x+1)}/{(2x-1)^3(x-1)^3}
a(n)=2^n*(-99/16+29n/32+3n^2/32)+n^2+4n+6, n>1. [From R. J. Mathar, Aug 05 2008]
CROSSREFS
Sequence in context: A116789 A116783 A116739 * A294796 A116753 A294762
KEYWORD
nonn,easy
AUTHOR
Lara Pudwell, Feb 26 2006
STATUS
approved