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 A304982 #12 Aug 14 2019 19:21:09
%S A304982 1,2,5,19,137,3053,822526
%N A304982 Number of unlabeled clutters (connected antichains) spanning up to n vertices with singleton edges allowed.
%C A304982 The initial terms 1, 2, 5, 19 are the same as A304981 but the remaining terms differ.
%F A304982 Partial sums of A304983.
%e A304982 Non-isomorphic representatives of the a(3) = 19 clutters:
%e A304982 {}
%e A304982 {{1}}
%e A304982 {{1,2}}
%e A304982 {{1,2,3}}
%e A304982 {{2},{1,2}}
%e A304982 {{1,3},{2,3}}
%e A304982 {{3},{1,2,3}}
%e A304982 {{1},{2},{1,2}}
%e A304982 {{1,2},{1,3},{2,3}}
%e A304982 {{3},{1,2},{2,3}}
%e A304982 {{3},{1,3},{2,3}}
%e A304982 {{2},{3},{1,2,3}}
%e A304982 {{1},{2},{3},{1,2,3}}
%e A304982 {{2},{3},{1,2},{1,3}}
%e A304982 {{3},{1,2},{1,3},{2,3}}
%e A304982 {{2},{3},{1,3},{2,3}}
%e A304982 {{1},{2},{3},{1,3},{2,3}}
%e A304982 {{2},{3},{1,2},{1,3},{2,3}}
%e A304982 {{1},{2},{3},{1,2},{1,3},{2,3}}
%Y A304982 Cf. A048143, A198085, A261006, A304912, A304981, A304982, A304983, A304984, A304985, A304986.
%K A304982 nonn,more
%O A304982 0,2
%A A304982 _Gus Wiseman_, May 23 2018
%E A304982 a(5)-a(6) from _Andrew Howroyd_, Aug 14 2019