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%I A361506 #20 Dec 03 2023 18:39:47
%S A361506 1,3,8,19,45,102,232,524,1181,2659,5984,13466,30300,68177,153400,
%T A361506 345151,776590,1747330,3931495,8845865,19903197,44782195,100759939,
%U A361506 226709865,510097199,1147718699,2582367075,5810325919,13073233320,29414774972,66183243689,148912298302
%N A361506 a(n) = floor( (4/5)*( (9/4)^(n+1)-1 ) ).
%D A361506 N. Tokuda, An Improved Shellsort, IFIP Transactions, A-12 (1992) 449-457.
%H A361506 Marcin Ciura, <a href="https://doi.org/10.1007/3-540-44669-9_12">Best Increments for the Average Case of Shellsort</a>, in R. Freivalds,  (ed.), Fundamentals of Computation Theory: 13th International Symposium, FCT 2001, Riga, Latvia, August 2001, Lecture Notes in Computer Science, vol. 2138, Springer, pp. 106-117.
%t A361506 A361506[n_]:=Floor[4/5((9/4)^(n+1)-1)];Array[A361506,50,0] (* _Paolo Xausa_, Dec 02 2023 *)
%Y A361506 Other sequences used for Shell sort: A003462, A033622, A036562, A036564, A036569, A055875, A055876, A108870, A361507.
%K A361506 nonn
%O A361506 0,2
%A A361506 _N. J. A. Sloane_, Mar 20 2023, at the suggestion of _Don Knuth_.
%E A361506 Some terms corrected by _Paolo Xausa_, Dec 02 2023

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