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 A095423 #9 May 10 2013 12:45:34 %S A095423 0,1,42,15654,1073421588,4611685989440629944, %T A095423 85070591730234615704434641716516893512, %U A095423 28948022309329048855892746252171976959574390130279817915318273546782086570304 %N A095423 Number of proper T_0-covers of an n-set. %C A095423 The next term has 154 decimal digits. %F A095423 a(n) = Sum(Stirling1(n, k)*A007537(k), k=1..n). %F A095423 a(n) = Sum((2*Stirling1(n+1, k+1)-Stirling1(n, k))*2^(2^k-2), k=0..n). %o A095423 (PARI) %o A095423 a(n)=sum(k=0,n, (2*stirling(n+1, k+1, 1) - stirling(n, k,1 )) * 2^(2^k-2) ); %o A095423 vector(10,n,a(n)) /* show terms */ %Y A095423 Row sums of A095422, A095421. %K A095423 easy,nonn %O A095423 1,3 %A A095423 Goran Kilibarda, _Vladeta Jovovic_, Jun 04 2004