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 A162820 #4 Mar 31 2012 12:38:25
%S A162820 12,15,20,30,40,60,84,90,120,140,165,180,240,300,340,390,540,660,840,
%T A162820 1140,1740,3540
%N A162820 Positive numbers n such that 60*n/(60+n) are integers.
%t A162820 f[a_,b_]:=(a*b)/(a+b); a=60;lst={};Do[If[f[a,n]==IntegerPart[f[a,n]], AppendTo[lst,n]],{n,9!}];lst
%Y A162820 Cf. A162688, A162689, A162690, A162691, A162692, A162693, A162694, A162817, A162818, A162819
%Y A162820 Cf. A127730. [From _Franklin T. Adams-Watters_, Aug 07 2009]
%K A162820 nonn,fini,full
%O A162820 1,1
%A A162820 _Vladimir Joseph Stephan Orlovsky_, Jul 13 2009
%E A162820 Keywords fini,full added by _R. J. Mathar_, Jul 31 2009