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 A103207 #13 May 01 2015 12:32:57
%S A103207 1,2,144,1036800,1463132160000,668986161758208000000,
%T A103207 148045794139338685651353600000000,
%U A103207 22147346968743318573346465338485637120000000000
%N A103207 a(n)=(-1)^floor(n/2)/det(M_n) where M_n is the n X n matrix of terms 1/(i+j)! i and j ranging from 1 to n.
%F A103207 a(n)=(1/2^n)*{prod(k=1, n, (2*k)!/k!)}^2.
%F A103207 a(n) ~ A * 2^(2*n^2 + 2*n + 5/12) * n^(n^2 + n + 1/12) / exp(3*n^2/2 + n + 1/12), where A = A074962 = 1.2824271291... is the Glaisher-Kinkelin constant. - _Vaclav Kotesovec_, May 01 2015
%p A103207 seq(mul(mul(k+j,j=1..n), k=0..n), n=0..7); # _Zerinvary Lajos_, Jun 01 2007
%t A103207 Table[1/2^n*(Product[(2*k)!/k!,{k,1,n}])^2,{n,0,10}] (* _Vaclav Kotesovec_, May 01 2015 *)
%t A103207 Table[2^(2*n^2 + n - 1/12) * Glaisher^3 * BarnesG[n+3/2]^2 / (E^(1/4) * Pi^(n+1/2)),{n,0,10}] (* _Vaclav Kotesovec_, May 01 2015 *)
%o A103207 (PARI) a(n)=(1/2^n)*prod(k=1,n,(2*k)!/k!)^2
%Y A103207 Cf. A062381.
%K A103207 nonn
%O A103207 0,2
%A A103207 _Benoit Cloitre_, Mar 19 2005