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 A256509 #12 Apr 22 2015 12:06:26
%S A256509 -1,-1,-1,713,620448401733239439359975
%N A256509 a(n) = (n!)! - n! - 1.
%C A256509 Term a(5) has 199 decimal digits. - _Michael De Vlieger_, Mar 31 2015
%e A256509 a(3) = (3!)! - 3! - 1 = 720 - 6 - 1 = 713.
%t A256509 Table[(n!)! - n! - 1, {n, 0, 5}] (* _Michael De Vlieger_, Mar 31 2015 *)
%K A256509 sign
%O A256509 0,4
%A A256509 _Assoul Abdelkarim_, Mar 31 2015