OFFSET
0,4
COMMENTS
The labeled case is A323817.
FORMULA
Inverse Euler transform of A317795.
EXAMPLE
Non-isomorphic representatives of the a(3) = 6 set-systems:
{{1,2,3}}
{{1,3},{2,3}}
{{2,3},{1,2,3}}
{{1,2},{1,3},{2,3}}
{{1,3},{2,3},{1,2,3}}
{{1,2},{1,3},{2,3},{1,2,3}}
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Jan 30 2019
STATUS
approved