OFFSET
19,1
LINKS
Alois P. Heinz, Table of n, a(n) for n = 19..200
EXAMPLE
a(19) = 8 because there are 8 9-element subsets of {1, 2, ..., 19} having pairwise coprime elements: {1,3,4,5,7,11,13,17,19}, {1,3,5,7,8,11,13,17,19}, {1,3,5,7,11,13,16,17,19}, {1,2,3,5,7,11,13,17,19}, {1,4,5,7,9,11,13,17,19}, {1,2,5,7,9,11,13,17,19}, {1,5,7,8,9,11,13,17,19}, {1,5,7,9,11,13,16,17,19}.
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Mar 02 2011
STATUS
approved