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A116826
Number of permutations of length n which avoid the patterns 2143, 2431, 3124.
0
1, 2, 6, 21, 73, 244, 794, 2553, 8179, 26192, 83906, 268883, 861815, 2762484, 8855204, 28385839, 90992639, 291683062, 935010104, 2997239539, 9607859097, 30798658994, 98727239296, 316477019741, 1014489059421, 3252015115894
OFFSET
1,2
LINKS
FORMULA
G.f.: A(x) = -{x(4x^5-11x^4+18x^3-15x^2+6x-1)}/{(4x^3-7x^2+5x-1)(x-1)^3}
CROSSREFS
Sequence in context: A226431 A116802 A294697 * A116760 A116828 A294764
KEYWORD
nonn,easy
AUTHOR
Lara Pudwell, Feb 26 2006
STATUS
approved