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 A321256 #6 Nov 01 2018 18:22:54 %S A321256 1,1,0,2,0,0,4,0,0,0,6,1,0,0,0,13,5,0,0,0,0,23,12,2,0,0,0,0,49,36,11, %T A321256 0,0,0,0,0,100,95,39,5,0,0,0,0,0,220,262,143,32,1,0,0,0,0,0 %N A321256 Regular triangle where T(n,k) is the number of non-isomorphic connected set systems of weight n with density -1 <= k <= n-2. %C A321256 A set system is a finite set of finite nonempty sets. The density of a set system is the sum of sizes of each part (weight) minus the number of parts minus the number of vertices. %e A321256 Triangle begins: %e A321256 1 %e A321256 1 0 %e A321256 2 0 0 %e A321256 4 0 0 0 %e A321256 6 1 0 0 0 %e A321256 13 5 0 0 0 0 %e A321256 23 12 2 0 0 0 0 %e A321256 49 36 11 0 0 0 0 0 %e A321256 100 95 39 5 0 0 0 0 0 %e A321256 220 262 143 32 1 0 0 0 0 0 %Y A321256 First column is A321228. Row sums are A007718. %Y A321256 Cf. A007716, A030019, A056156, A283877, A293607, A300913, A319557, A321155, A321253, A321254. %K A321256 nonn,tabl,more %O A321256 1,4 %A A321256 _Gus Wiseman_, Nov 01 2018