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A116846
Number of permutations of length n which avoid the patterns 321, 12354.
0
1, 1, 2, 5, 14, 41, 113, 277, 607, 1212, 2245, 3913, 6488, 10319, 15845, 23609, 34273, 48634, 67641, 92413, 124258, 164693, 215465, 278573, 356291, 451192, 566173, 704481, 869740, 1065979, 1297661, 1569713, 1887557, 2257142, 2684977, 3178165, 3744438, 4392193
OFFSET
0,3
FORMULA
G.f.: 1+x(x^8-4x^7+3x^6+6x^5-13x^4+14x^3-12x^2+5x-1)/(x-1)^7.
For n >= 3, a(n) = (n^6 + 9n^5 - 5n^4 - 405n^3 + 1804n^2 - 684n - 2160)/720. - Franklin T. Adams-Watters, Sep 16 2006
CROSSREFS
Sequence in context: A243881 A358416 A225691 * A080558 A116844 A116851
KEYWORD
nonn,easy
AUTHOR
Lara Pudwell, Feb 26 2006
STATUS
approved