OFFSET
1,3
COMMENTS
Also the number of maximal subsets of {1..n} containing n such that every orderless pair of (not necessarily distinct) elements has a different sum.
EXAMPLE
The a(2) = 1 through a(9) = 18 subsets:
{1,2} {1,3} {1,2,4} {1,2,5} {1,2,6} {2,3,7} {3,5,8} {4,6,9}
{2,3} {1,3,4} {1,4,5} {1,3,6} {2,4,7} {4,5,8} {5,6,9}
{2,3,5} {1,4,6} {2,6,7} {1,2,4,8} {1,2,4,9}
{2,4,5} {1,5,6} {3,4,7} {1,2,6,8} {1,2,6,9}
{2,3,6} {4,5,7} {1,3,4,8} {1,2,7,9}
{2,5,6} {4,6,7} {1,3,7,8} {1,3,4,9}
{3,4,6} {1,2,5,7} {1,5,6,8} {1,3,8,9}
{3,5,6} {1,3,6,7} {1,5,7,8} {1,4,8,9}
{2,3,6,8} {1,6,7,9}
{2,4,7,8} {1,6,8,9}
{2,3,5,9}
{2,3,7,9}
{2,4,5,9}
{2,4,8,9}
{2,6,7,9}
{2,6,8,9}
{3,4,7,9}
{3,5,8,9}
MATHEMATICA
fasmax[y_]:=Complement[y, Union@@(Most[Subsets[#]]&/@y)];
Table[Length[fasmax[Select[Subsets[Range[n]], MemberQ[#, n]&&UnsameQ@@Subtract@@@Subsets[Union[#], {2}]&]]], {n, 0, 10}]
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Gus Wiseman, Jun 02 2019
STATUS
approved