OFFSET
0,2
FORMULA
Binomial transform of A369194.
EXAMPLE
The a(0) = 1 through a(2) = 7 loop-graphs:
{} {} {}
{{1}} {{1}}
{{2}}
{{1,2}}
{{1},{2}}
{{1},{1,2}}
{{2},{1,2}}
MATHEMATICA
Table[Length[Select[Subsets[Subsets[Range[n], {1, 2}]], Length[#]<=Length[Union@@#]&]], {n, 0, 5}]
CROSSREFS
A006125 counts simple graphs, also loop-graphs if shifted left.
KEYWORD
nonn
AUTHOR
Gus Wiseman, Jan 17 2024
STATUS
approved