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 A114633 #20 Sep 03 2017 15:24:03
%S A114633 1,3,18,70,555,2961,31108,213228,2799765,23455135,369569046,
%T A114633 3659001138,67261566463,768390239085,16142775951240,209002145031256,
%U A114633 4939689441079593,71478733600689723,1877081987610245530,30021068112289683870,867211878275933435091,15190660464818580038473
%N A114633 a(n) = (n+1)*(n+2)/2 * Sum_{k=0..floor(n/2)} n!/(n-2*k)!.
%C A114633 Formula was found by _Paul D. Hanna_.
%C A114633 Related to logarithmic numbers A002104.
%H A114633 Vincenzo Librandi, <a href="/A114633/b114633.txt">Table of n, a(n) for n = 0..450</a>
%F A114633 a(n) = A087208(n)*(n+1)*(n+2)/2. - _Paul D. Hanna_
%F A114633 E.g.f.: exp(x)/(1-x^2)*(x^2/2) (with offset 2). - _Zerinvary Lajos_, Apr 03 2009
%p A114633 a:= n-> (n+1)*(n+2)/2*sum(n!/(n-2*k)!,k=0..floor(n/2)): seq(a(n), n=0..20);
%t A114633 Rest[Rest[With[{nn=25}, CoefficientList[Series[Exp[x]/(1 - x^2)(x^2/2), {x, 0, nn}], x] Range[0, nn]!]]] (* _Vincenzo Librandi_, Sep 03 2017 *)
%Y A114633 Cf. A002104, A087208.
%K A114633 nonn
%O A114633 0,2
%A A114633 _Creighton Dement_, Feb 17 2006
%E A114633 More terms from _Vincenzo Librandi_, Sep 03 2017