OFFSET
1,2
COMMENTS
FORMULA
For n > 0, a(n) = A326081(n)/2.
EXAMPLE
The a(6) = 28 sets:
{} {2} {2,4} {2,3,6} {2,3,4,6} {2,3,4,5,6}
{3} {2,5} {2,4,5} {2,3,5,6}
{4} {2,6} {2,4,6} {2,4,5,6}
{5} {3,4} {2,5,6} {3,4,5,6}
{6} {3,5} {3,4,5}
{3,6} {3,4,6}
{4,5} {3,5,6}
{4,6} {4,5,6}
{5,6}
MATHEMATICA
Table[Length[Select[Subsets[Range[2, n]], SubsetQ[#, Select[Times@@@Subsets[#, {2}], #<=n&]]&]], {n, 0, 10}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Jun 06 2019
EXTENSIONS
Terms a(21) and beyond from Andrew Howroyd, Aug 24 2019
STATUS
approved