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 A181895 #12 Apr 04 2012 12:15:08
%S A181895 4,28,176,1258,10070,90692,907184,9979181,119750111,1556754911,
%T A181895 21794572379,326918591535,5230697470143,88921857013919,
%U A181895 1600593426385151,30411275101997759,608225502043759679
%N A181895 Difference between maximum and minimum positive value y in solutions to x^2 - y^2 = n!.
%F A181895 a(n) = A139174(n) - A038202(n).
%t A181895 cc = {}; Do[f = n!/4; x = Max[Select[Divisors[f], # <= Sqrt[f] &]]; kk = f/x - x; kkk = ((n! - 4)/4); AppendTo[cc, kkk - kk], {n, 4, 20}]; cc
%K A181895 nonn,easy
%O A181895 4,1
%A A181895 _Artur Jasinski_, Mar 31 2012