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 A174826 #10 Jan 18 2024 18:57:24
%S A174826 1,3,1260,471517200,550527639742080000,
%T A174826 5190428913555819988454400000000,
%U A174826 850897011688550259860209488988778496000000000000,4613713285873452716084822982464795709127827429408768000000000000000000
%N A174826 Hankel transform of median Euler numbers A000657.
%F A174826 a(n) = Product_{k=0..n} ((k+1)*(4k+1)*(4k+3)*floor((2k+3)/2))^(n-k).
%F A174826 a(n) ~ sqrt(Gamma(1/4)) * 2^(2*n^2 + 7*n/2 + 9/8) * n^(n*(2*n+3) + 47/48) * Pi^(n + 3/4) / (A^(7/4) * exp(3*n*(n+1) - 7/48)), where A is the Glaisher-Kinkelin constant A074962. - _Vaclav Kotesovec_, Feb 24 2019
%t A174826 Table[Product[((k+1)*(4*k+1)*(4*k+3)*Floor[(2*k+3)/2])^(n-k), {k,0,n}], {n,0,10}] (* _Vaclav Kotesovec_, Feb 24 2019 *)
%K A174826 easy,nonn
%O A174826 0,2
%A A174826 _Paul Barry_, Mar 30 2010
%E A174826 a(5) and following corrected by _Georg Fischer_, Jan 18 2024