%I
%S 2,8,4096,1152921504606846976,
%T 2348542582773833227889480596789337027375682548908319870707290971532209025114608443463698998384768703031934976
%N a(n) = (...((2^3)^4)^...)^n.
%C Another kind of exponential factorial.
%C See crossreferences for other possible definitions of exponential factorials.
%C Some other terms of the sequence can be computed, but they are quite large and it wouldn't be very convenient to display them.
%C The next term has 759 digits.  _Harvey P. Dale_, Oct 22 2019
%F a(n) = 2^(n!/2) for n >= 2.  _Karl W. Heuer_, Nov 25 2014
%e a(4) = 4096, as (2^3)^4 = 4096.
%p expfact:= proc(n::integer) local i,res; res:=2; for i from 3 to n do res:=(res)^i od; res end proc; seq(expfact(n), n=2..7);
%t nxt[{n_,a_}]:={n+1,a^(n+1)}; NestList[nxt,{2,2},4][[All,2]] (* _Harvey P. Dale_, Oct 22 2019 *)
%Y Cf. A124075, A049384.
%K nonn
%O 2,1
%A Pierre Karpman (pierre.karpman(AT)laposte.net), Oct 28 2007
