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 A186941 #6 Aug 04 2019 18:21:50
%S A186941 1,3,30,632,24512,1768448,243236864,64959283200,34084592025600,
%T A186941 35395409601888256,73066365170086838272,300608105396373834170368,
%U A186941 2468626449866096479911804928,40500446023029046169942454435840,1328092178371231300789305464410079232
%N A186941 a(n)=2^C(n,2)*(2(4^n-n*2^n)-1).
%C A186941 Hankel transform of A186940.
%F A186941 a(n)=2^C(n,2)*A186942(n).
%t A186941 Table[2^Binomial[n,2] (2(4^n-n*2^n)-1),{n,0,20}] (* _Harvey P. Dale_, Aug 04 2019 *)
%K A186941 nonn,easy
%O A186941 0,2
%A A186941 _Paul Barry_, Mar 01 2011