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 A101407 #9 Aug 22 2016 14:17:46
%S A101407 4,4,16,4096,281474976710656,
%T A101407 1766847064778384329583297500742918515827483896875618958121606201292619776
%N A101407 a(n) = 4^(n!).
%e A101407 a(3) = 4^(3!) = 4096.
%t A101407 a=4;lst={};Do[a=a^n;AppendTo[lst,a],{n,1,7}];lst (* _Vladimir Joseph Stephan Orlovsky_, May 26 2009 *)
%t A101407 4^Range[0,5]! (* _Harvey P. Dale_, Aug 22 2016 *)
%K A101407 nonn
%O A101407 0,1
%A A101407 _Parthasarathy Nambi_, Jan 15 2005