|
| |
|
|
A136529
|
|
a(n) = the smallest possible number of positive divisors of the sum of any two distinct positive divisors of n.
|
|
1
| |
|
|
2, 3, 2, 4, 2, 4, 2, 3, 2, 6, 2, 4, 2, 3, 2, 6, 2, 6, 2, 3, 2, 8, 2, 4, 2, 3, 2, 8, 2, 6, 2, 3, 2, 4, 2, 4, 2, 3, 2, 8, 2, 6, 2, 3, 2, 10, 2, 4, 2, 3, 2, 8, 2, 4, 2, 3, 2, 12, 2, 4, 2, 3, 2, 4, 2, 6, 2, 3, 2, 12, 2, 4, 2, 3, 2, 4, 2, 10, 2, 3, 2, 12, 2, 4, 2, 3, 2, 12, 2, 4, 2, 3, 2, 4, 2, 6, 2, 3, 2, 8, 2, 8
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 2,1
|
|
|
COMMENTS
| There are d(n)*(d(n)-1)/2 sums of pairs of distinct positive divisors of n, where d(n) = number of positive divisors of n.
|
|
|
EXAMPLE
| The positive divisors of 6 are 1,2,3,6. Letting d(m) = the number of positive divisors of m: d(1+2)=2; d(1+3)=3; d(1+6)=2; d(2+3)=2; d(2+6)=4; d(3+6)=3. The least of these values is 2, so a(6) = 2.
|
|
|
PROG
| (PARI) { a(n) = d=divisors(n); m=numdiv(n+1); for(i=1, #d, for(j=i+1, #d, m=min(m, numdiv(d[i]+d[j])); )); m } [From Max Alekseyev (maxale(AT)gmail.com), Apr 27 2009]
|
|
|
CROSSREFS
| Cf. A136528.
Sequence in context: A025477 A080189 A076399 * A113982 A101743 A060937
Adjacent sequences: A136526 A136527 A136528 * A136530 A136531 A136532
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| Leroy Quet Jan 03 2008
|
|
|
EXTENSIONS
| Extended by Max Alekseyev (maxale(AT)gmail.com), Apr 27 2009
|
| |
|
|
