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 A066209 #7 Aug 03 2014 14:27:52
%S A066209 0,0,2,0,0,2,6,0,8,0,10,8,12,4,5,0,16,8,18,0,5,12,22,8,0,16,8,8,28,20,
%T A066209 30,0,32,24,10,8,36,28,17,0,40,2,42,12,35,36,46,32,41,0,2,40,52,8,10,
%U A066209 32,14,48,58,20,60,52,26,0,10,56,66,20,38,50,70,8,72,64,50,64,10,74,78
%N A066209 A053041(n)-10^(n-1).
%C A066209 a(n) = 0 iff n is of form 2^i*5^j (cf. A003592).
%t A066209 lst = {}; Do[z = n - Mod[10^n/10, n]; If[z == n, z = 0]; AppendTo[lst, z], {n, 79}]; lst (* _Arkadiusz Wesolowski_, Apr 02 2012 *)
%K A066209 easy,nonn
%O A066209 1,3
%A A066209 _Vladeta Jovovic_, Dec 17 2001