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 A054442 #4 Mar 31 2012 13:20:01 %S A054442 1,3,9,22,54,123,281,618,1362,2934,6330,13452,28620,60243,126921, %T A054442 265282,554874,1153506,2399390,4966740,10286196,21219038,43790154, %U A054442 90076452,185353204,380364108,780786516,1599015192,3275589144 %N A054442 Second convolution of A001405 (central binomial numbers). %F A054442 a(2*k)= -3*2^(2*k+1)+binomial(2*(k+1), k+1)*(4*k+7)/2, a(2*k+1)= -3*4^(k+1)+binomial(2*(k+2), k+2)*(2*k+5)/2, k >= 0. %F A054442 a(n)= A054336(n+2, 2) (third column of convolution triangle). G.f.: (1/(1-x-x^2*c(x^2)))^3, with c(x) the g.f. for the Catalan numbers A000108. %Y A054442 Cf. A000108, A001405, A054336, A045621. %K A054442 easy,nonn %O A054442 0,2 %A A054442 _Wolfdieter Lang_, Mar 27 2000