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A294764
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Number of permutations of [n] avoiding {2143, 3142, 1234}.
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0
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1, 1, 2, 6, 21, 73, 247, 821, 2704, 8868, 29030, 94960, 310531, 1015359, 3319829, 10854379, 35488838, 116031978, 379370276, 1240362982, 4055405209, 13259272613, 43351600979, 141739396705, 463421329340, 1515170329456, 4953896123490, 16196916164572, 52956316947055, 173142311541835
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OFFSET
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0,3
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LINKS
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Table of n, a(n) for n=0..29.
D. Callan, T. Mansour, Enumeration of small Wilf classes avoiding 1324 and two other 4-letter patterns, arXiv:1705.00933 [math.CO] (2017), Table 2 No 111.
Index entries for linear recurrences with constant coefficients, signature (7,-18,24,-19,9,-2).
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FORMULA
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4*a(n) = n+1-n^2 -A175005(n) +A175005(n+1), n>0. - R. J. Mathar, Nov 05 2021
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MAPLE
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((x^3-2*x^2+3*x-1)^2)/((2*x^3-3*x^2+4*x-1)*(x-1)^3) ;
taylor(%, x=0, 40) ;
gfun[seriestolist](%) ;
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CROSSREFS
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Sequence in context: A116826 A116760 A116828 * A116837 A116781 A047106
Adjacent sequences: A294761 A294762 A294763 * A294765 A294766 A294767
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KEYWORD
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nonn,easy
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AUTHOR
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R. J. Mathar, Nov 08 2017
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STATUS
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approved
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