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 A131623 #15 Sep 04 2015 08:44:20
%S A131623 1,1,7,9,31,223,442,1529,6559,66111,159952,742503,3047656,19094286,
%T A131623 245173117,761328969,3935539271,20213664703,117323673136,897132508439,
%U A131623 15791065424134,56649181720176,353387529508691,1955231849465423
%N A131623 Number of blocks in all partitions of n-set with distinct block sizes.
%H A131623 Alois P. Heinz, <a href="/A131623/b131623.txt">Table of n, a(n) for n = 1..300</a>
%F A131623 E.g.f.: Sum(x^n/(n!+x^n),n=1..inf)*Product(1+x^n/n!,n=1..inf).
%p A131623 A131623 := proc(n) local su,i ; su := add(x^i/(i!+x^i),i=1..n+1) ; for i from 1 to n do su := taylor(su*(1+x^i/i!),x=0,n+1) ; od: n!*coeftayl(su,x=0,n) ; end: seq(A131623(n),n=1..30) ; # _R. J. Mathar_, Oct 25 2007
%t A131623 nn=20;p=Product[1+y x^i/i!,{i,1,nn}];Range[0,nn]! CoefficientList[Series[D[p,y]/.y->1,{x,0,nn}],x] (* _Geoffrey Critzer_, Aug 30 2012 *)
%Y A131623 Cf. A044048, A007837.
%K A131623 easy,nonn
%O A131623 1,3
%A A131623 _Vladeta Jovovic_, Sep 02 2007
%E A131623 More terms from _R. J. Mathar_, Oct 25 2007