OFFSET
0,5
COMMENTS
LINKS
S. R. Finch, Monoids of natural numbers, March 17, 2009.
EXAMPLE
The subset {2,4,6} has 6 = 4 + 2 so is counted under a(6).
The subset {1,2,4,7} has 7 = 4 + 2 + 1 so is counted under a(7).
The subset {1,4,5,8} has 5 = 4 + 1 so is counted under a(8).
The a(0) = 0 through a(6) = 17 subsets:
. . . {1,2,3} {1,3,4} {1,4,5} {1,5,6}
{1,2,3,4} {2,3,5} {2,4,6}
{1,2,3,5} {1,2,3,6}
{1,2,4,5} {1,2,4,6}
{1,3,4,5} {1,2,5,6}
{2,3,4,5} {1,3,4,6}
{1,2,3,4,5} {1,3,5,6}
{1,4,5,6}
{2,3,4,6}
{2,3,5,6}
{2,4,5,6}
{1,2,3,4,6}
{1,2,3,5,6}
{1,2,4,5,6}
{1,3,4,5,6}
{2,3,4,5,6}
{1,2,3,4,5,6}
MATHEMATICA
Table[Length[Select[Subsets[Range[n]], MemberQ[#, n]&&Intersection[#, Total/@Subsets[#, {2, Length[#]}]]!={}&]], {n, 0, 10}]
CROSSREFS
First differences of A364534.
KEYWORD
nonn
AUTHOR
Gus Wiseman, Aug 26 2023
STATUS
approved