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A116819
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Number of permutations of length n which avoid the patterns 2431, 4123, 4231.
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0
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1, 2, 6, 21, 76, 274, 978, 3463, 12201, 42869, 150415, 527426, 1848905, 6480722, 22715293, 79617891, 279063942, 978133274, 3428414441, 12016810218, 42119714480, 147632440224, 517461749617, 1813738775801, 6357278456431
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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) = -{(3x^3-8x^2+5x-1)x}/{3x^4-14x^3+16x^2-7x+1}
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MATHEMATICA
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LinearRecurrence[{7, -16, 14, -3}, {1, 2, 6, 21}, 30] (* Harvey P. Dale, Mar 31 2023 *)
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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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