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 A056072 #27 Aug 14 2025 20:27:10 %S A056072 1,2,15,3814279 %N A056072 a(n) = floor(e^e^ ... ^e), with n e's. %C A056072 The next term is too large to include. %C A056072 From _Vladimir Reshetnikov_, Apr 27 2013: (Start) %C A056072 a(4) = 2331504399007195462289689911...2579139884667434294745087021 (1656521 decimal digits in total), given by initial segment of A085667. %C A056072 a(5) has more than 10^10^6 decimal digits. %C A056072 a(6) has more than 10^10^10^6 decimal digits. (End) %p A056072 p:= n-> `if`(n=0, 1, exp(1)^p(n-1)): %p A056072 a:= n-> floor(p(n)): %p A056072 seq(a(n), n=0..3); # _Alois P. Heinz_, Jul 20 2024 %t A056072 Floor[NestList[Exp, 1, 3]] (* _Vladimir Reshetnikov_, Apr 29 2013 *) %o A056072 (PARI) A056072(n,f=floor)=f(exp(if(n>0,A056072(n-1,x->x)))) \\ _M. F. Hasler_, May 01 2013 %Y A056072 Cf. A001113, A004002, A003417, A064107, A159825, A073226, A073227, A085667, A096232, A225064, A225053. %K A056072 nonn %O A056072 0,2 %A A056072 _Robert G. Wilson v_, Jul 26 2000