OFFSET
21,1
COMMENTS
A set is called nondividing if no element divides the sum of any nonempty subset of the other elements.
LINKS
Eric Weisstein's World of Mathematics, Nondividing Set
EXAMPLE
a(21) = 2 because there are two 5-element nondividing subsets of {1,2,...,21}: {12,16,18,19,21}, {12,14,18,20,21}.
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Mar 10 2011
STATUS
approved