2,1

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.

Table of n, a(n) for n=2..96.

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 maximum of these values is 4, so a(6) = 4.

Cf. A136529.

Sequence in context: A064004 A195849 A087827 * A263252 A276334 A225486

Adjacent sequences: A136525 A136526 A136527 * A136529 A136530 A136531

nonn

Leroy Quet, Jan 03 2008

More terms from Sean A. Irvine, Feb 28 2011

approved