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 A116710 Number of permutations of length n which avoid the patterns 1423, 3421. 1
 1, 2, 6, 22, 86, 337, 1299, 4910, 18228, 66640, 240550, 859295, 3043525, 10705182, 37441618, 130351650, 452119862, 1563402141, 5392828631, 18564966510, 63807048144, 219015409556, 750968486726, 2572756726459, 8808011192329, 30138217809470, 103077794599470 (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 (11,-47,99,-109,63,-18,2). FORMULA G.f.: x*(1 - 9*x + 31*x^2 - 49*x^3 + 37*x^4 - 14*x^5 + 2*x^6) / ((1 - x)*(1 - 3*x + x^2)^2*(1 - 4*x + 2*x^2)). PROG (PARI) Vec(x*(1 - 9*x + 31*x^2 - 49*x^3 + 37*x^4 - 14*x^5 + 2*x^6) / ((1 - x)*(1 - 3*x + x^2)^2*(1 - 4*x + 2*x^2)) + O(x^30)) \\ Colin Barker, Oct 23 2017 CROSSREFS Sequence in context: A165528 A116709 A165529 * A165530 A116707 A116704 Adjacent sequences: A116707 A116708 A116709 * A116711 A116712 A116713 KEYWORD nonn,easy AUTHOR Lara Pudwell, Feb 26 2006 STATUS approved

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Last modified September 13 10:55 EDT 2024. Contains 375904 sequences. (Running on oeis4.)