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A116772
Number of permutations of length n which avoid the patterns 1234, 1243, 1432.
0
1, 2, 6, 21, 76, 278, 1021, 3756, 13827, 50916, 187512, 690593, 2543444, 9367525, 34500756, 127067006, 467990629, 1723620240, 6348133335, 23380322908, 86110274536, 317146150489, 1168056674504, 4301979997337, 15844292751908
OFFSET
1,2
FORMULA
G.f.: A(x) = -{x(x-1)(x^4+3x^3-5x^2+4x-1)}/{-13x^4+21x^3-17x^2+7x-1+2x^5}
CROSSREFS
Sequence in context: A116798 A279560 A116821 * A131792 A144904 A376791
KEYWORD
nonn,easy
AUTHOR
Lara Pudwell, Feb 26 2006
STATUS
approved