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 A116400 #2 Mar 30 2012 18:59:14 %S A116400 0,0,1,1,5,5,21,21,84,84,330,330,1287,1287,5005,5005,19448,19448, %T A116400 75582,75582,293930,293930,1144066,1144066,4457400,4457400,17383860, %U A116400 17383860,67863915,67863915,265182525 %N A116400 E.g.f. Bessel_I(2,2x)+Bessel_I(3,2x)+Bessel_I(4,2x). %C A116400 T(n,2) in number triangle A116399. Double of A002054. %F A116400 G.f.: (1+x)*x^2*c(x^2)^4/(2-c(x^2)), c(x) the g.f. of A000108; a(n)=C(n+1,n/2-1)(1+(-1)^n)/2 + C(n,(n-1)/2-1)(1-(-1)^n)/2. %o A116400 (PARI) a(n)=n=n\2; binomial(2*n+1,n-1) %Y A116400 A002054(n)=a(2n)=a(2n+1). %K A116400 easy,nonn %O A116400 0,5 %A A116400 _Paul Barry_, Feb 13 2006