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 A073581 #7 Dec 08 2022 20:46:18 %S A073581 1,1,2,36,48708493958471199415506599153950129703565945470976 %N A073581 Factorials successively exponentiated. %C A073581 a(5) > 10^(10^50). %F A073581 a(n) = n!^a(n - 1) starting with a(0)=0!=1. %e A073581 a(3) = 36 because 3!^(2!^(1!^0!)) = 36 %t A073581 a[0] := 1 a[n_Integer] := n!^a[n - 1] %Y A073581 Cf. A049384, A358972 (exponents left to right). %K A073581 easy,nonn %O A073581 0,3 %A A073581 Jon Kongsvold (Jon.Kongsvold(AT)idi.ntnu.no), Aug 28 2002 %E A073581 Edited by _Henry Bottomley_, Jul 13 2003