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 A173098 #5 Nov 21 2013 12:49:59
%S A173098 1,2,2,6,18,198,6930,2737350,37936933650,207693292716721350,
%T A173098 15758493330480878908260133650,
%U A173098 6545866736124132578837836330405530973356721350
%N A173098 a(1)=1, a(2)=2, a(n)=2*a(n-2)*a(n-1)-a(n-1).
%t A173098 a=1;b=2;lst={a,b};Do[c=2*a*b-b;AppendTo[lst,c];a=b;b=c,{n,12}];lst
%t A173098 RecurrenceTable[{a[1]==1,a[2]==2,a[n]==2a[n-2]a[n-1]-a[n-1]},a,{n,14}] (* _Harvey P. Dale_, Jan 27 2012 *)
%Y A173098 Cf. A173093, A173094, A173096, A173097
%K A173098 nonn
%O A173098 1,2
%A A173098 _Vladimir Joseph Stephan Orlovsky_, Feb 09 2010