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 A059523 #16 Dec 17 2022 12:48:34 %S A059523 1,2,2,36,19020,2010231696,9219217412568364176, %T A059523 170141181796805105960861096082778425120, %U A059523 57896044618658097536026644159052312977171804852352892309392604715987334365792 %N A059523 Number of n-element unlabeled ordered T_0-antichains without isolated vertices; number of T_1-hypergraphs (without empty edge and without multiple edges) on n labeled vertices. %H A059523 V. Jovovic, <a href="/A059523/a059523.pdf">T_1-hyper graphs on a labeled 3-set</a> %H A059523 Goran Kilibarda and Vladeta Jovovic, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL7/Kilibarda/kili2.html">Antichains of Multisets</a>, J. Integer Seqs., Vol. 7, 2004. %H A059523 Goran Kilibarda and Vladeta Jovovic, <a href="https://arxiv.org/abs/1411.4187">Enumeration of some classes of T_0-hypergraphs</a>, arXiv:1411.4187 [math.CO], 2014. %F A059523 a(n) = A059052(n)/2. %e A059523 Number of k-element T_1-hipergraphs (without empty edge and without multiple edges) on 3 labeled vertices is %e A059523 C(7,k)-6*C(5,k)+6*C(4,k)+3*C(3,k)-6*C(2,k)+2*C(1,k),k=0..7; so a(3)=2+11+15+7+1=36=2^7-6*2^5+6*2^4+3*2^3-6*2^2+2*2. %Y A059523 Cf. A003465, A059201, A059052, A326961. %K A059523 nonn %O A059523 0,2 %A A059523 _Vladeta Jovovic_ and Goran Kilibarda, Jan 20 2001; revised Jun 03 2004