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 A116709 Number of permutations of length n which avoid the patterns 2341, 4213. 1
 1, 2, 6, 22, 86, 336, 1290, 4870, 18164, 67234, 247786, 911120, 3346618, 12286942, 45104548, 165573482, 607817410, 2231360192, 8191763970, 30074097062, 110410946820, 405353571346, 1488185247962, 5463619641904, 20058759689642, 73642362774478, 270365534734372 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Colin Barker, Table of n, a(n) for n = 1..1000 Darla Kremer and Wai Chee Shiu, Finite transition matrices for permutations avoiding pairs of length four patterns, Discrete Math. 268 (2003), 171-183. MR1983276 (2004b:05006). See Table 1. Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005. Wikipedia, Permutation classes avoiding two patterns of length 4 Index entries for linear recurrences with constant coefficients, signature (8,-22,25,-10,2). FORMULA G.f.: -x*(2*x^4-7*x^3+12*x^2-6*x+1) / (2*x^5-10*x^4+25*x^3-22*x^2+8*x-1). a(n) = 8*a(n-1) - 22*a(n-2) + 25*a(n-3) - 10*a(n-4) + 2*a(n-5) for n>5. - Colin Barker, Oct 20 2017 PROG (PARI) Vec(x*(1 - 6*x + 12*x^2 - 7*x^3 + 2*x^4) / (1 - 8*x + 22*x^2 - 25*x^3 + 10*x^4 - 2*x^5) + O(x^30)) \\ Colin Barker, Oct 20 2017 CROSSREFS Sequence in context: A165526 A165527 A165528 * A165529 A116710 A165530 Adjacent sequences: A116706 A116707 A116708 * A116710 A116711 A116712 KEYWORD nonn,easy AUTHOR Lara Pudwell, Feb 26 2006 STATUS approved

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Last modified September 19 04:40 EDT 2024. Contains 376004 sequences. (Running on oeis4.)