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 A055130 #14 Jan 03 2024 15:09:23
%S A055130 1,1,2,1,1,4,9,10,6,3,1,1,7,29,87,181,287,364,365,290,187,97,39,13,4,
%T A055130 1,1,10,72,417,1973,7745,25830,74017,183420,395311,744495,1229807,
%U A055130 1787135,2289925,2591162,2591163,2289929,1787148,1229846,744592,395498
%N A055130 Triangle T(n,k) of numbers of k-covers of an unlabeled n-set, k=1..2^n-1.
%H A055130 Andrew Howroyd, <a href="/A055130/b055130.txt">Table of n, a(n) for n = 1..2036</a> (rows 1..10)
%F A055130 T(n,n) = A368186(n). - _Andrew Howroyd_, Jan 03 2024
%e A055130 Triangle begins:
%e A055130 [1] 1;
%e A055130 [2] 1, 2, 1;
%e A055130 [3] 1, 4, 9, 10, 6, 3, 1;
%e A055130 [4] 1, 7, 29, 87, 181, 287, 364, 365, 290, 187, 97, 39, 13, 4, 1;
%e A055130 ...
%e A055130 There are 9 3-covers of an unlabeled 3-set: {{1,2},{2,3},{1,2,3}}, {{1,2},{2,3},{1,3}}, {{1,2},{3},{1,2,3}}, {{1},{1,2},{1,2,3}}, {{1,2},{2,3},{3}}, {{1,2},{2},{2,3}}, {{1},{2},{1,2,3}}, {{1},{2},{1,3}} and {{1},{2},{3}}.
%o A055130 (PARI) \\ G(n,m) defined in A368186.
%o A055130 row(n)={my(m=2^n-1); Vec(G(n,m) - G(n-1,m))} \\ _Andrew Howroyd_, Jan 03 2024
%Y A055130 Row sums give A055621.
%Y A055130 Columns k=1..3 are A000012, A014616(n-1), A055195.
%Y A055130 Cf. A052265, A368186.
%K A055130 nonn,tabf
%O A055130 1,3
%A A055130 _Vladeta Jovovic_, Jun 14 2000