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A116743
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Number of permutations of length n which avoid the patterns 3421, 4123, 4213.
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0
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1, 2, 6, 21, 75, 267, 950, 3384, 12065, 43034, 153524, 547744, 1954328, 6973114, 24880601, 88776363, 316763410, 1130246720, 4032847433, 14389658085, 51343944371, 183201075822, 653682454214, 2332414030833, 8322321077596
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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(x^3-2x^2+3x-1)(x-1)^2}/{(x^2-x+1)(x^4-5x^3+10x^2-6x+1)}
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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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