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 A121340 #8 Mar 14 2015 17:38:11
%S A121340 1,2,3,1,4,9,1,16,81,1,256,6561,1,65536,43046721,1,4294967296,
%T A121340 1853020188851841,1,18446744073709551616,
%U A121340 3433683820292512484657849089281,1,340282366920938463463374607431768211456,11790184577738583171520872861412518665678211592275841109096961
%N A121340 List of triples {1^(2^k), 2^(2^k), 3^(2^k)} for k>0.
%t A121340 NestList[{#[[ -3]]^2, #[[ -2]]^2, #[[ -1]]^2} &, {1, 2, 3}, 7] // Flatten (* _Robert G. Wilson v_, Sep 02 2006 *)
%t A121340 Flatten[Table[{1,2,3}^2^k,{k,0,8}]] (* _Harvey P. Dale_, May 24 2012 *)
%Y A121340 Cf. A000012, A001146, A011764.
%K A121340 nonn
%O A121340 1,2
%A A121340 Marius Solend (mariussolend(AT)hotmail.com), Aug 29 2006
%E A121340 More terms from _Robert G. Wilson v_, Sep 02 2006