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 A036562 a(n) = 4^(n+1) + 3*2^n + 1. 12
 1, 8, 23, 77, 281, 1073, 4193, 16577, 65921, 262913, 1050113, 4197377, 16783361, 67121153, 268460033, 1073790977, 4295065601, 17180065793, 68719869953, 274878693377, 1099513200641, 4398049656833, 17592192335873, 70368756760577 (list; graph; refs; listen; history; text; internal format)
 OFFSET -1,2 LINKS Vincenzo Librandi, Table of n, a(n) for n = -1..1000 Robert Sedgewick, Analysis of shellsort and related algorithms, Fourth European Symposium on Algorithms, Barcelona, September, 1996. FORMULA a(n) = (1/2)*(A028401(n+4) + 1) for n > -1. G.f.: (1+x-19*x^2+20*x^3)/(x*(1-x)*(1-2*x)*(1-4*x)). [Colin Barker, Mar 09 2012] MATHEMATICA CoefficientList[Series[x*(1+x-19*x^2+20*x^3)/(x*(1-x)*(1-2*x)*(1-4*x)), {x, 0, 30}], x] (* Vincenzo Librandi, Apr 24 2012 *) PROG (MAGMA) [1]cat[4^(n+1)+3*2^n+1:n in [0..30]]; // Vincenzo Librandi, Apr 24 2012 (PARI) a(n)=4^(n+1)+3*2^n+1 \\ Charles R Greathouse IV, Apr 24 2012 CROSSREFS Sequences used for Shell sort: A003462, A033622, A036562, A036564, A036569, A055875, A055876. Sequence in context: A059209 A099274 A208633 * A320310 A303720 A304414 Adjacent sequences:  A036559 A036560 A036561 * A036563 A036564 A036565 KEYWORD nonn,easy AUTHOR STATUS approved

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Last modified October 19 16:17 EDT 2019. Contains 328223 sequences. (Running on oeis4.)