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 A308440 #15 Aug 11 2019 00:03:59 %S A308440 1,5,1,37,15,1,365,223,30,1,4501,3675,745,50,1,66605,68071,18450,1865, %T A308440 75,1,1149877,1411515,479101,64750,3920,105,1,22687565,32512663, %U A308440 13260030,2244501,181650,7322,140,1,503589781,825175275,393017185,79948050,8103711,436590,12558,180,1 %N A308440 Matrix product of triangle of Stirling numbers of second kind A008277 and square of unsigned Lah triangle A105278. %C A308440 Also the number of k-dimensional flats of the extended Catalan arrangement of dimension n consisting of hyperplanes x_i - x_j = d (1 <= i < j <= n, -2 <= d <= 2). %H A308440 Robert Gill, <a href="https://doi.org/10.1016/S0012-365X(97)00187-8">The number of elements in a generalized partition semilattice</a>, Discrete mathematics 186.1-3 (1998): 125-134. %H A308440 N. Nakashima and S. Tsujie, <a href="https://arxiv.org/abs/1904.09748">Enumeration of Flats of the Extended Catalan and Shi Arrangements with Species</a>, arXiv:1904.09748 [math.CO], 2019. %F A308440 E.g.f.: exp((exp(x)-1)*y/(3-2exp(x))). %e A308440 Triangle begins: %e A308440 1; %e A308440 5, 1; %e A308440 37, 15, 1; %e A308440 365, 223, 30, 1; %e A308440 4501, 3675, 745, 50, 1; %e A308440 ... %Y A308440 Cf. A008277, A105278, A050351 (first column), A109092 (row sums). %K A308440 nonn,tabl %O A308440 1,2 %A A308440 _Shuhei Tsujie_, May 27 2019