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A116776
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Number of permutations of length n which avoid the patterns 2134, 3142, 3421.
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0
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1, 2, 6, 21, 73, 239, 734, 2133, 5924, 15859, 41202, 104433, 259312, 632815, 1521646, 3612653, 8482796, 19726315, 45481962, 104071145, 236519400, 534249447, 1200095206, 2682257381, 5967445988, 13220446179, 29175578594, 64156073953
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OFFSET
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1,2
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LINKS
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FORMULA
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G.f.: A(x) = {(x^6-14x^5+37x^4-45x^3+27x^2-8x+1)x}/{(2x-1)^4(x-1)^2}.
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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