%I #13 Jun 09 2016 03:10:14
%S 1,4,12,48,144,440,1816,6816,25816,101856,397944,1573464,6274560,
%T 25071152,100180872,400625360
%N a(n) = A253086(2^n-1).
%C In trying to understand A253086, this subsequence looked like the best place to attack it. But there is unfortunately no obvious formula even here.
%H <a href="/index/Ce#cell">Index entries for sequences related to cellular automata</a>
%Y Cf. A253086.
%K nonn,more
%O 0,2
%A _N. J. A. Sloane_, Feb 12 2015
%E a(10)-a(15) from _Lars Blomberg_, Jun 09 2016