|
| |
|
|
A159070
|
|
Count of numbers k in the range 1 < k <= n such that set of proper divisors of k is a subset of the set of proper divisors of n.
|
|
2
|
|
|
|
0, 1, 2, 3, 3, 5, 4, 6, 5, 6, 5, 10, 6, 8, 8, 9, 7, 11, 8, 12, 10, 10, 9, 16, 10, 11, 11, 13, 10, 17, 11, 15, 13, 13, 13, 19, 12, 14, 14, 19, 13, 19, 14, 18, 19, 16, 15, 24, 16, 19, 17, 19, 16, 22, 18, 23, 18, 18, 17, 28, 18, 20, 23, 23, 20, 24, 19, 23, 21, 26, 20, 31, 21, 23, 25, 25
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
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.
|
|
|
LINKS
|
Table of n, a(n) for n=1..76.
|
|
|
FORMULA
|
a(n) = A158973(n) - 1.
If p = prime, element of A000040, a(p) = A158973(p) - 1 = A036234(p) - 1 = A000720(p).
|
|
|
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
|
Cf. A158973, A000040, A036234, A000720.
Sequence in context: A086898 A123031 A271709 * A088241 A163126 A304818
Adjacent sequences: A159067 A159068 A159069 * A159071 A159072 A159073
|
|
|
KEYWORD
|
nonn
|
|
|
AUTHOR
|
Jaroslav Krizek, Apr 04 2009
|
|
|
EXTENSIONS
|
Edited and extended by R. J. Mathar, Apr 06 2009
|
|
|
STATUS
|
approved
|
| |
|
|
