OFFSET
1,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = A187262(n,2).
EXAMPLE
a(4) = 9 because there are 9 nonempty subsets of {1,2,3,4} with <=2 pairwise coprime elements: {1}, {2}, {3}, {4}, {1,2}, {1,3}, {1,4}, {2,3}, {3,4}.
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Mar 07 2011
STATUS
approved