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 A025617 #17 Jul 06 2025 10:01:17
%S A025617 1,4,5,16,20,25,64,80,100,125,256,320,400,500,625,1024,1280,1600,2000,
%T A025617 2500,3125,4096,5120,6400,8000,10000,12500,15625,16384,20480,25600,
%U A025617 32000,40000,50000,62500,65536,78125,81920,102400,128000,160000,200000,250000
%N A025617 Numbers of form 4^i*5^j, with i, j >= 0.
%H A025617 Amiram Eldar, <a href="/A025617/b025617.txt">Table of n, a(n) for n = 1..10000</a>
%F A025617 Sum_{n>=1} 1/a(n) = (4*5)/((4-1)*(5-1)) = 5/3. - _Amiram Eldar_, Sep 24 2020
%F A025617 a(n) ~ exp(sqrt(2*log(4)*log(5)*n)) / sqrt(20). - _Vaclav Kotesovec_, Sep 24 2020
%F A025617 a(n) = 4^A025646(n) * 5^A025650(n). - _R. J. Mathar_, Jul 06 2025
%t A025617 n = 10^5; Flatten[Table[4^i*5^j, {i, 0, Log[4, n]}, {j, 0, Log[5, n/4^i]}]] // Sort (* _Amiram Eldar_, Sep 24 2020 *)
%Y A025617 Subsequence of A003592.
%K A025617 easy,nonn
%O A025617 1,2
%A A025617 _David W. Wilson_