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 A121348 #2 Mar 31 2012 10:29:10 %S A121348 1,12,456,9360,155520,21772800,1146700800,44503603200,11860515072000, %T A121348 1237663494144000,107797432393728000,36342886035456000000, %U A121348 6476053728774389760000,1089563850990959984640000 %N A121348 Difference between (n!)^2 and the next smaller factorial. %e A121348 a(3)=12 because the difference between (3!)^2=36 and the next smaller factorial 4!=24 is 12. %Y A121348 Cf. A121347 [Largest number k such that (n!)^2-k!>0]. %K A121348 nonn %O A121348 2,2 %A A121348 _Hugo Pfoertner_, Aug 15 2006