%I

%S 3,27,443426488243037769948249630619149892803

%N a(0)=3 and a(n+1)=a(n)^a(n).

%C If the initial term is 2 the sequence is 2, 4, 256, 256^256, ...

%t NestList[#^#&,3,2] (* _Harvey P. Dale_, Nov 06 2011 *)

%Y Cf. A000312.

%K bref,nonn

%O 0,1

%A _Benoit Jubin_, Jul 02 2009