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A116838
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Number of permutations of length n which avoid the patterns 1342, 3421, 4312.
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0
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1, 2, 6, 21, 72, 233, 719, 2146, 6260, 17968, 50967, 143278, 399960, 1110203, 3067479, 8442903, 23163006, 63371999, 172967309, 471115792, 1280844662, 3476636122, 9423007521, 25506378316, 68958653982, 186231636833
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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.: x*(x^9 -8x^8 +34x^7 -97x^6 +183x^5 -205x^4 +135x^3 -52x^2 +11x -1)/((x^2-3x+1)^2 (2x-1)^2 (x-1)^3).
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MATHEMATICA
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CoefficientList[Series[(x^9 - 8 x^8 + 34 x^7 - 97 x^6 + 183 x^5 - 205 x^4 + 135 x^3 - 52 x^2 + 11 x - 1)/((x^2 - 3 x + 1)^2 (2 x - 1)^2 (x - 1)^3), {x, 0, 30}], x] (* Wesley Ivan Hurt, Dec 28 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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