OFFSET
0,4
COMMENTS
Row-sums of left portion of A054548.
FORMULA
Inverse binomial transform of A369193.
EXAMPLE
The a(0) = 1 through a(3) = 4 graphs:
{} . {{1,2}} {{1,2},{1,3}}
{{1,2},{2,3}}
{{1,3},{2,3}}
{{1,2},{1,3},{2,3}}
MATHEMATICA
Table[Length[Select[Subsets[Subsets[Range[n], {2}]], Length[Union@@#]==n&&Length[#]<=n&]], {n, 0, 5}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Jan 17 2024
STATUS
approved