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 A187442 #10 Dec 08 2023 11:19:03
%S A187442 1,3,20,126,924,6435,48620,352716,2704156,20058300,155117520,
%T A187442 1166803110,9075135300,68923264410,538257874440,4116715363800,
%U A187442 32247603683100,247959266474052,1946939425648112,15033633249770520,118264581564861424
%N A187442 A trisection of A001405 (central binomial coefficients): binomial(3*n,floor(3*n/2)), n>=0.
%C A187442 For the trisection of sequences see a comment and a reference under A187357.
%F A187442 a(n) = binomial(3*n,floor(3*n/2)), n>=0.
%F A187442 O.g.f.: G0(x^2) + 3*x*G2(x^2) with G0(x) and G2(x) the o.g.f.s of A187363 and A187365, respectively.
%t A187442 Table[Binomial[3n,Floor[(3n)/2]],{n,0,20}] (* _Harvey P. Dale_, Dec 23 2012 *)
%Y A187442 A187443 binomial(3*n+1,floor((3*n+1)/2)),
%Y A187442 A187444 binomial(3*n+2,floor((3*n+2)/2))/2.
%K A187442 nonn,easy
%O A187442 0,2
%A A187442 _Wolfdieter Lang_, Mar 10 2011