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 A220874 Number of permutations of [n+1] avoiding 2413, 3142, 1324, 4231. 1
 1, 2, 6, 20, 64, 194, 562, 1570, 4258, 11266, 29186, 74242, 185858, 458754, 1118210, 2695170, 6430722, 15204354, 35651586, 82968578, 191758338, 440401922, 1005584386, 2283798530, 5161091074, 11609833474, 26004684802, 58015612930, 128949682178 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Andrei Asinowski and Toufik Mansour, Separable d-Permutations and Guillotine Partitions, arXiv:0803.3414 [math.CO], 2008. Andrei Asinowski and Toufik Mansour, Separable d-Permutations and Guillotine Partitions, Annals of Combinatorics 14 (1) pp.17-43 Springer, 2010. Index entries for linear recurrences with constant coefficients, signature (9,-32,56,-48,16). FORMULA Andrei Asinowski and Toufik Mansour give a g.f. G.f. -(-7*x+20*x^2-26*x^3+12*x^4+2*x^5+1)/((x-1)*(2*x-1)^4). - R. J. Mathar, Jan 04 2013 a(n) = 2+(n-1)*(n^2+n+42)*2^(n-4)/3 for n>0. - R. J. Mathar, Jan 30 2013 (see Maple section). MAPLE A220874 := proc(n)     if n = 0 then         1;     else         2+(n-1)*(n^2+n+42)*2^(n-4)/3 ;     end if; end proc: # R. J. Mathar, Jan 30 2013 MATHEMATICA a[0] = 1; a[n_] := 2 + (n - 1)*(n^2 + n + 42)*2^(n - 4)/3; Table[a[n], {n, 0, 28}] (* Jean-François Alcover, Dec 01 2017, after R. J. Mathar *) CROSSREFS Sequence in context: A193235 A199102 A053730 * A273902 A181301 A302612 Adjacent sequences:  A220871 A220872 A220873 * A220875 A220876 A220877 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Dec 27 2012 STATUS approved

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Last modified June 24 01:07 EDT 2021. Contains 345404 sequences. (Running on oeis4.)