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 A137160 #2 Mar 30 2012 18:37:09
%S A137160 1,2,4,12,64,664,13856,584668,49751520,8509625760,2919099754336,
%T A137160 2005648412219832,2758163973596156000,7588978611071894509464,
%U A137160 41769719229784446295570112,459846172005153447271276789620
%N A137160 G.f.: 1 = Sum_{n>=0} a(n)*x^n*(1-x)/(1+x)^(2^n).
%C A137160 Equals the unsigned row sums of triangle A137156.
%o A137160 (PARI) {a(n)=polcoeff(1-sum(k=0, n-1, a(k)*x^k*(1-x)/(1+x+x*O(x^n))^(2^k) ), n)}
%Y A137160 Cf. A137156; A001192, A137157, A137158, A137159.
%K A137160 nonn
%O A137160 0,2
%A A137160 _Paul D. Hanna_, Jan 24 2008