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 A193684 #21 Aug 02 2021 06:33:14
%S A193684 1,3,8,17,17,-78,-585,-2021,-1710,29395,231413,856264,-346979,
%T A193684 -30019585,-232782792,-834712259,2313820717,59793779314,469729578123,
%U A193684 1597321309383,-9914171906614,-206169178856073,-1697255630380351,-5677886943413120,55801423903125353
%N A193684 Alternating row sums of Sheffer triangle A143496 (4-restricted Stirling2 numbers).
%C A193684 In order to have A143496 as a lower triangular Sheffer matrix one uses row and column offsets 0 (not 4).
%H A193684 Seiichi Manyama, <a href="/A193684/b193684.txt">Table of n, a(n) for n = 0..591</a>
%F A193684 E.g.f.: exp(-exp(x)+4*x+1).
%F A193684 a(n) = exp(1) * Sum_{k>=0} (-1)^k * (k + 4)^n / k!. - _Ilya Gutkovskiy_, Dec 20 2019
%F A193684 a(0) = 1; a(n) = 4 * a(n-1) - Sum_{k=0..n-1} binomial(n-1,k) * a(k). - _Seiichi Manyama_, Aug 02 2021
%e A193684 With offset [0,0] row n=3 of A143496 is [64,61,15,1], hence a(3)=64-61+15-1=17.
%o A193684 (PARI) my(x='x+O('x^30)); Vec(serlaplace(exp(-exp(x)+4*x+1))) \\ _Michel Marcus_, Aug 02 2021
%Y A193684 Cf. A143496, A193683 (3-restricted Stirling2 case), A196835, A293037, A346739.
%K A193684 sign,easy
%O A193684 0,2
%A A193684 _Wolfdieter Lang_, Oct 06 2011