OFFSET
1,3
COMMENTS
Here proper divisors include 1 but not the argument (k or n, respectively) in the divisor set, as defined in A032741.
FORMULA
EXAMPLE
a(8) = 6 admits the following 6 k: 2 {1}, 3 {1}, 4 {1, 2}, 5 {1}, 7 {1}, 8 {1, 2, 4} with subsets of the proper divisors {1, 2, 4} for n = 8.
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Apr 04 2009
EXTENSIONS
Edited and extended by R. J. Mathar, Apr 06 2009
STATUS
approved