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%I #15 Jul 26 2024 13:01:15
%S 1,1,4,18,142,3100,823042
%N Number of unlabeled antichains of finite sets spanning n vertices with singleton edges allowed.
%F a(n) = A304996(n) - A304996(n-1) for n > 0. - _Andrew Howroyd_, Aug 13 2019
%F Euler transform of A304983. - _Andrew Howroyd_, Aug 14 2019
%e Non-isomorphic representatives of the a(3) = 18 antichains:
%e {{1,2,3}}
%e {{3},{1,2}}
%e {{3},{1,2,3}}
%e {{1,3},{2,3}}
%e {{1},{2},{3}}
%e {{2},{3},{1,3}}
%e {{2},{3},{1,2,3}}
%e {{3},{1,2},{2,3}}
%e {{3},{1,3},{2,3}}
%e {{1,2},{1,3},{2,3}}
%e {{1},{2},{3},{2,3}}
%e {{1},{2},{3},{1,2,3}}
%e {{2},{3},{1,2},{1,3}}
%e {{2},{3},{1,3},{2,3}}
%e {{3},{1,2},{1,3},{2,3}}
%e {{1},{2},{3},{1,3},{2,3}}
%e {{2},{3},{1,2},{1,3},{2,3}}
%e {{1},{2},{3},{1,2},{1,3},{2,3}}
%Y Cf. A006126, A261005, A304996, A304997, A304998, A304999, A305000, A305001.
%Y See also A374399.
%K nonn,more
%O 0,3
%A _Gus Wiseman_, May 23 2018
%E a(5)-a(6) from _Andrew Howroyd_, Aug 13 2019
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