OFFSET
0,3
COMMENTS
Two or more numbers are pairwise coprime if no pair of them has a common divisor > 1.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..38
EXAMPLE
The a(4) = 10 set partitions: 1|2|3|4, 14|2|3, 13|2|4, 12|3|4, 1|23|4, 1|2|34, 134|2, 123|4, 14|23, 12|34.
MATHEMATICA
spsu[_, {}]:={{}}; spsu[foo_, set:{i_, ___}]:=Join@@Function[s, Prepend[#, s]&/@spsu[Select[foo, Complement[#, Complement[set, s]]=={}&], Complement[set, s]]]/@Cases[foo, {i, ___}];
Table[Length[spsu[Select[Subsets[Range[n]], Length[#]==1||CoprimeQ@@#&], Range[n]]], {n, 10}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Jan 08 2019
EXTENSIONS
a(14)-a(15) from Alois P. Heinz, Jan 08 2019
a(16) from Alois P. Heinz, Mar 26 2020
a(17)-a(24) from Giovanni Resta, Mar 27 2020
a(25)-a(28) from Alois P. Heinz, Aug 03 2023
STATUS
approved