OFFSET
0,3
FORMULA
a(n) = Sum_{k=0..n} binomial(binomial(n,2),k).
EXAMPLE
The a(0) = 1 through a(3) = 8 graphs:
{} {} {} {}
{{1,2}} {{1,2}}
{{1,3}}
{{2,3}}
{{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[#]<=n&]], {n, 0, 5}]
PROG
(Python)
from math import comb
def A369192(n): return sum(comb(comb(n, 2), k) for k in range(n+1)) # Chai Wah Wu, Jul 14 2024
CROSSREFS
Counting only covered vertices gives A369193.
KEYWORD
nonn
AUTHOR
Gus Wiseman, Jan 17 2024
STATUS
approved