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 A166232 #7 May 08 2016 00:40:38
%S A166232 1,1,3,20,272,7424,405504,44302336,9680453632,4230542786560,
%T A166232 3697657604210688,6463791365183504384,22598414411798807576576,
%U A166232 158015104883301198495481856,2209780998563745292895322636288
%N A166232 a(n) = A166231(n)/4^n.
%C A166232 a(n+1) is the Hankel transform of A068764.
%H A166232 G. C. Greubel, <a href="/A166232/b166232.txt">Table of n, a(n) for n = 0..70</a>
%F A166232 a(n) = 2^C(n,2)*Sum_{k=0..floor(n/2)} C(n,2k)*2^(-k).
%F A166232 a(n) = A166231(n)/4^n.
%t A166232 Table[2^(Binomial[n, 2])*Sum[Binomial[n, 2 k]*2^(-k), {k, 0, Floor[n/2]}], {n, 0, 25}] (* _G. C. Greubel_, May 07 2016 *)
%Y A166232 Cf. A068764, A166231.
%K A166232 easy,nonn
%O A166232 0,3
%A A166232 _Paul Barry_, Oct 09 2009