OFFSET
0,3
FORMULA
EXAMPLE
Non-isomorphic representatives of the a(0) = 1 through a(3) = 22 set-systems:
{{}} {{}{1}} {{}{12}} {{}{123}}
{{}{1}{2}} {{}{1}{23}}
{{}{2}{12}} {{}{3}{123}}
{{}{1}{2}{12}} {{}{1}{2}{3}}
{{}{23}{123}}
{{}{1}{3}{23}}
{{}{2}{3}{123}}
{{}{3}{13}{23}}
{{}{1}{23}{123}}
{{}{3}{23}{123}}
{{}{1}{2}{3}{23}}
{{}{1}{2}{3}{123}}
{{}{2}{3}{13}{23}}
{{}{1}{3}{23}{123}}
{{}{2}{3}{23}{123}}
{{}{3}{13}{23}{123}}
{{}{1}{2}{3}{13}{23}}
{{}{1}{2}{3}{23}{123}}
{{}{2}{3}{13}{23}{123}}
{{}{1}{2}{3}{12}{13}{23}}
{{}{1}{2}{3}{13}{23}{123}}
{{}{1}{2}{3}{12}{13}{23}{123}}
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Gus Wiseman, Jul 30 2019
EXTENSIONS
a(5)-a(7) from Andrew Howroyd, Aug 10 2019
STATUS
approved