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 A108870 Tokuda's good set of increments for Shell sort. 2
 1, 4, 9, 20, 46, 103, 233, 525, 1182, 2660, 5985, 13467, 30301, 68178, 153401, 345152, 776591, 1747331, 3931496, 8845866, 19903198, 44782196, 100759940, 226709866, 510097200, 1147718700, 2582367076, 5810325920, 13073233321, 29414774973 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Empirically better for the average running time than currently known sequences of increments, except A102549 (and only a few terms of that sequence are known). REFERENCES Marcin Ciura, Best Increments for the Average Case of Shellsort, 13th International Symposium on Fundamentals of Computation Theory, Riga, Latvia, Aug 22 2001; Lecture Notes in Computer Science 2001; 2138: 106-117. N. Tokuda, An Improved Shellsort, IFIP Transactions, A-12 (1992) 449-457. LINKS Alois P. Heinz, Table of n, a(n) for n = 0..1000 Marcin Ciura, Best Increments for the Average Case of Shellsort FORMULA a(n) = ceiling( (9 * (9/4)^n - 4) / 5). CROSSREFS Other sequences used for Shell sort: A003462, A033622, A036562, A036564, A036569, A055875, A055876. Sequence in context: A144686 A144685 A109110 * A111587 A161221 A130045 Adjacent sequences:  A108867 A108868 A108869 * A108871 A108872 A108873 KEYWORD easy,nonn AUTHOR Jud McCranie, Jul 13 2005 STATUS approved

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Last modified October 22 10:24 EDT 2019. Contains 328317 sequences. (Running on oeis4.)