OFFSET
0,6
COMMENTS
For example, the set {4,7,9,10} has choice (2,7,3,5) so is counted under a(10).
EXAMPLE
The a(0) = 0 through a(10) = 14 subsets (A = 10):
. . 2 23 34 235 256 2357 3578 2579 237A
345 356 2567 5678 4579 267A
456 3457 5679 279A
3567 5789 347A
4567 357A
367A
378A
467A
479A
567A
579A
678A
679A
789A
MATHEMATICA
Table[Length[Select[Subsets[Range[n], {PrimePi[n]}], MemberQ[#, n]&&Length[Select[Tuples[If[#==1, {}, First/@FactorInteger[#]]&/@#], UnsameQ@@#&]]>0&]], {n, 0, 10}]
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Gus Wiseman, Feb 28 2024
STATUS
approved