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 A162693 #6 Sep 25 2019 11:00:23 %S A162693 6,15,20,30,45,60,70,120,150,195,270,420,870 %N A162693 Strictly positive numbers n such that 30*n/(30+n) are integers. %C A162693 The 30th row of A127730. %C A162693 The ansatz 30*n/(30+n)=j (any integer j) yields n=30*j/(30-j) which demonstrates that the sequence is finite if n>=0. [R. J. Mathar, Jul 13 2009] %t A162693 f[a_,b_]:=(a*b)/(a+b); a=30;lst={};Do[If[f[a,n]==IntegerPart[f[a,n]],AppendTo[lst,n]],{n,9!}];lst %t A162693 Select[Range[1000],IntegerQ[(30#)/(30+#)]&] (* _Harvey P. Dale_, Sep 25 2019 *) %Y A162693 Cf. A162688, A162689, A162690, A162691, A162692 %Y A162693 Cf. A127730. [From _Franklin T. Adams-Watters_, Aug 07 2009] %K A162693 nonn,fini,full %O A162693 1,1 %A A162693 _Vladimir Joseph Stephan Orlovsky_, Jul 10 2009 %E A162693 Edited by _R. J. Mathar_, Jul 13 2009