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 A126207 #5 Aug 24 2012 10:49:58 %S A126207 0,1,1,1,1,1,2,1,1,2,2,1,1,1,3,3,3,2,2,1,2,2,3,3,3,2,2,4,2,3,5,3,2,3, %T A126207 3,2,5,4,3,5,2,6,5,1,2,1,6,5,6,4,4,3,2,4,9,9,9,4,4,2,5,2,4,5,5,7,8,6, %U A126207 5,5,5,7,6,11,7,7,5,5,6,7,6,8,8,10,5,6,7,8,9,4,10,7,4,8,10,9,6,5,6,10,6 %N A126207 Number of 5's in decimal expansion of 5^n. %p A126207 P:=proc(n) local i,k,x,y,w,cont; y:=5; k:=y; for i from 0 by 1 to n do x:=y^i; cont:=0; while x>0 do w:=x-trunc(x/10)*10; if w=k then cont:=cont+1; fi; x:=trunc(x/10); od; print(cont); od; end: P(100); %Y A126207 Cf. A065710, A126205, A126206, A126208, A126209, A126210, A126211. %K A126207 nonn,base %O A126207 0,7 %A A126207 _Paolo P. Lava_ and _Giorgio Balzarotti_, Dec 20 2006