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 A025642 #11 Jul 06 2025 10:16:25 %S A025642 0,1,0,2,1,3,0,2,4,1,3,5,0,2,4,6,1,3,5,7,0,2,4,6,8,1,3,5,7,0,9,2,4,6, %T A025642 8,1,10,3,5,7,0,9,2,11,4,6,8,1,10,3,12,5,7,0,9,2,11,4,13,6,8,1,10,3, %U A025642 12,5,14,7,0,9,2,11,4,13,6,15,8,1,10,3,12,5,14,7,0,16,9,2,11,4,13,6,15,8,1,17,10 %N A025642 Exponent of 3 (value of i) in n-th number of form 3^i*7^j. %H A025642 Robert Israel, <a href="/A025642/b025642.txt">Table of n, a(n) for n = 1..10000</a> %p A025642 N:= 10^9: # for 3^i * 7^j <= N %p A025642 R:= sort([seq(seq(3^i*7^j, j=0 .. ilog[7](N/3^i)),i=0..ilog[3](N))]): %p A025642 map(padic:-ordp,R,3); # _Robert Israel_, Jun 04 2025 %Y A025642 Cf. A003594. %K A025642 nonn %O A025642 1,4 %A A025642 _David W. Wilson_