%I #4 Apr 01 2018 13:41:20
%S 3,8,256,
%T 115792089237316195423570985008687907853269984665640564039457584007913129639936
%N a(0)=3 and a(n+1)=2^a(n).
%C Initializing at 0, 1, 2 or 4 gives A014221.
%t NestList[2^#&,3,3] (* _Harvey P. Dale_, Apr 01 2018 *)
%Y A000079 (powers of 2).
%K nonn
%O 0,1
%A _Benoit Jubin_, Jun 27 2009