OFFSET
0,9
LINKS
Wikipedia, Geometric mean
EXAMPLE
The a(1) = 1 through a(12) = 3 subsets:
{1} {2} {3} {4} {5} {6} {7} {8} {9} {10} {11} {12}
{2,8} {1,9} {3,6,12}
{3,4,9,12}
The a(18) = 7 subsets:
{18}
{2,18}
{8,18}
{1,8,9,18}
{2,3,8,9,18}
{6,12,16,18}
{2,3,4,9,12,18}
MATHEMATICA
Table[Length[Select[Subsets[Range[n]], MemberQ[#, n]&&IntegerQ[Mean[#]]&&IntegerQ[GeometricMean[#]]&]], {n, 0, 10}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Jul 16 2019
EXTENSIONS
More terms from David Wasserman, Aug 03 2019
STATUS
approved