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 A304983 #10 Aug 14 2019 19:19:55
%S A304983 1,1,3,14,118,2916,819473
%N A304983 Number of unlabeled clutters (connected antichains) spanning n vertices with singleton edges allowed.
%F A304983 Inverse Euler transform of A304997. - _Andrew Howroyd_, Aug 14 2019
%e A304983 Non-isomorphic representatives of the a(3) = 14 clutters:
%e A304983 {{1,2,3}}
%e A304983 {{1,3},{2,3}}
%e A304983 {{3},{1,2,3}}
%e A304983 {{1,2},{1,3},{2,3}}
%e A304983 {{3},{1,2},{2,3}}
%e A304983 {{3},{1,3},{2,3}}
%e A304983 {{2},{3},{1,2,3}}
%e A304983 {{1},{2},{3},{1,2,3}}
%e A304983 {{2},{3},{1,2},{1,3}}
%e A304983 {{3},{1,2},{1,3},{2,3}}
%e A304983 {{2},{3},{1,3},{2,3}}
%e A304983 {{1},{2},{3},{1,3},{2,3}}
%e A304983 {{2},{3},{1,2},{1,3},{2,3}}
%e A304983 {{1},{2},{3},{1,2},{1,3},{2,3}}
%Y A304983 Cf. A048143, A198085, A261006, A304912, A304981, A304982, A304983, A304984, A304985, A304986, A304997.
%K A304983 nonn,more
%O A304983 0,3
%A A304983 _Gus Wiseman_, May 23 2018
%E A304983 a(5)-a(6) from _Andrew Howroyd_, Aug 14 2019