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 A213065 #21 Aug 02 2025 12:16:20
%S A213065 -1,0,0,513,281474976378880,
%T A213065 752316384526264005099991383822237233803945956334136013765601092018187046026142190625
%N A213065 a(n) = n^n! - n!^n.
%C A213065 a(6) has 561 digits: 1.8573779... * 10^560.
%t A213065 Table[n^n! - n!^n, {n, 0, 4}] (* _T. D. Noe_, Jun 04 2012 *)
%o A213065 (PARI) a(n) = n^n! - n!^n \\ _Stefano Spezia_, Aug 02 2025
%Y A213065 Cf. A036740, A053986.
%K A213065 sign
%O A213065 0,4
%A A213065 _Pratik Jain_, Jun 04 2012
%E A213065 a(5) from _Stefano Spezia_, Aug 02 2025