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 A173097 #4 Sep 10 2016 13:47:04
%S A173097 1,2,3,10,57,1130,128763,291003250,74940902830737,
%T A173097 43616092563357042787250,6537258709293941644669222566000575763,
%U A173097 570259361950353096439107826720562074995499493885695588056250
%N A173097 a(1)=1, a(2)=2, a(n)=2*a(n-2)*a(n-1)-a(n-2).
%t A173097 a=1;b=2;lst={a,b};Do[c=2*a*b-a;AppendTo[lst,c];a=b;b=c,{n,11}];lst
%t A173097 RecurrenceTable[{a[1]==1,a[2]==2,a[n]==2a[n-2]a[n-1]-a[n-2]},a,{n,15}] (* _Harvey P. Dale_, Sep 10 2016 *)
%Y A173097 Cf. A173093, A173094, A173096
%K A173097 nonn
%O A173097 1,2
%A A173097 _Vladimir Joseph Stephan Orlovsky_, Feb 09 2010