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 A114561 #15 Jul 23 2024 08:39:49 %S A114561 0,1,4,256, %T A114561 13407807929942597099574024998205846127479365820592393377723561443721764030073546976801874298166903427690031858186486050853753882811946569946433649006084096 %N A114561 a(0) = 0; thereafter a(n+1) = 4^a(n). %C A114561 Or, define two sequences by q(0) = 0, p(n) = 2^q(n), q(n+1) = p(n)^2; sequence gives q(n). %C A114561 4-ish analog of A014221 and A014222. - _Henry Bottomley_, Feb 16 2006 %t A114561 NestList[4^# &, 0, 4] (* _Paolo Xausa_, Jul 23 2024 *) %Y A114561 Cf. A114560, A081651, A014221, A014222. %K A114561 nonn %O A114561 0,3 %A A114561 _Jeremy Gardiner_, Feb 15 2006