This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A226721 #9 Nov 02 2024 18:00:23 %S A226721 2,3,5,6,8,9,11,12,13,15,16,18,19,21,22,23,25,26,28,29,31,32,33,35,36, %T A226721 38,39,41,42,43,45,46,48,49,51,52,53,55,56,58,59,61,62,63,65,66,68,69, %U A226721 71,72,73,75,76,78,79,81,82,83,85,86,88,89,91,92,93,95 %N A226721 Position of 2^n in the joint ranking of all the numbers 2^j for j>=0 and 5^k for k>=1; complement of A123384. %H A226721 Clark Kimberling, <a href="/A226721/b226721.txt">Table of n, a(n) for n = 1..2000</a> %F A226721 a(n) = 1 + A066344(n). %F A226721 a(n) = 1 + floor(n*(1 + log_5(2))). %e A226721 The joint ranking of the powers of 2 and of 5 begins like this: 1, 2, 4, 5, 8, 16, 25, 32, 64, 125, 128, 256, 512. The numbers 2^n for n >= 1 are in positions 2, 3, 5, 6, 8, 9, 11, 12, 13. %t A226721 b = 2; c=5; Floor[1 + Range[0, 100]*(1 + Log[b, c])] (* A123384 *) %t A226721 Floor[1 + Range[1, 100]*(1 + Log[c, b])] (* A226721 *) %Y A226721 Cf. A123384, A226720. %K A226721 nonn,easy %O A226721 1,1 %A A226721 _Clark Kimberling_, Jun 16 2013