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 A126781 #7 Dec 24 2012 02:05:12
%S A126781 720,20160,514080,13608000,385363440,11760819840,386860668480,
%T A126781 13682898028800,518666099711760,20997894426949440,904827327153291360,
%U A126781 41367795437773022400,2000634709955550047280,102066613831917982920960
%N A126781 Number of functions f:{1,2,...,n}->{1,2,...,n} such that Im(f) contains 6 fixed elements.
%H A126781 Milan Janjic, <a href="http://www.pmfbl.org/janjic/">Enumerative Formulas for Some Functions on Finite Sets</a>
%F A126781 a(n)=n^n-6*(n-1)^n+15*(n-2)^n-20*(n-3)^n+15*(n-4)^n-6*(n-5)^n+(n-6)^n, (n=6,7,...)
%e A126781 a(7)=20160
%p A126781 a:=n->n^n-6*(n-1)^n+15*(n-2)^n-20*(n-3)^n+15*(n-4)^n-6*(n-5)^n+(n-6)^n;
%t A126781 Drop[Table[Sum[(-1)^k Binomial[6,k] (n-k)^n,{k,0,6}],{n,1,20}],5] (* _Geoffrey Critzer_, Dec 23 2012 *)
%Y A126781 Cf. A039621 (Lehmer-Comtet numbers of 2nd kind).
%K A126781 nonn
%O A126781 6,1
%A A126781 Aleksandar M. Janjic and _Milan Janjic_, Feb 18 2007