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 A152801 #2 Mar 30 2012 18:37:15
%S A152801 1,2,5,21,87,378,1682,7596,34688,159724,740243,3448579,16134813,
%T A152801 75760294,356811308,1684882778,7974184903,37815280813,179644013528,
%U A152801 854749753320,4072634928710,19429522879905,92799859650401
%N A152801 a(n) = A152800(n+1,2n) for n>=0.
%C A152801 Triangle A152800 gives a q-analog of the Euler numbers.
%o A152801 (PARI) {a(n)=polcoeff(polcoeff(1/sum(m=0,n+1,(-1)^m*x^(2*m)/prod(j=1,2*m,(q^j-1)/(q-1))+x*O(x^(2*n+2))),2*n+2,x)*prod(j=1,2*n+2,(q^j-1)/(q-1)),2*n,q)}
%Y A152801 Cf. A152800; A152802.
%K A152801 nonn
%O A152801 0,2
%A A152801 _Paul D. Hanna_, Dec 26 2008