A136167 a(n) = the number of divisors of n that are each not coprime to any adjacent (previous or following) divisor of n.

1, 0, 0, 1, 0, 1, 0, 2, 1, 1, 0, 2, 0, 1, 1, 3, 0, 3, 0, 2, 1, 1, 0, 4, 1, 1, 2, 2, 0, 3, 0, 4, 1, 1, 1, 5, 0, 1, 1, 3, 0, 3, 0, 2, 2, 1, 0, 6, 1, 3, 1, 2, 0, 5, 1, 3, 1, 1, 0, 6, 0, 1, 2, 5, 1, 3, 0, 2, 1, 3, 0, 6, 0, 1, 3, 2, 1, 3, 0, 5, 3, 1, 0, 5, 1, 1, 1, 4, 0, 5, 1, 2, 1, 1, 1, 8, 0, 3, 2, 5, 0, 3, 0, 4, 3

Offset

1,8

Links

Diana Mecum, Table of n, a(n) for n = 1..1000

Example

The divisors of 28 are 1,2,4,7,14,28. Among adjacent pairs of divisors, 1 and 2 are coprime and 4 and 7 are coprime. Therefore there are a(28) =2 divisors that are each not next to any divisor they are coprime to. (These two divisors are 14 and 28.)

Crossrefs

Cf. A136164, A136165, A136166.

Sequence in context: A252736 A351416 A253559 * A140748 A185305 A259875

Adjacent sequences: A136164 A136165 A136166 * A136168 A136169 A136170

Keyword

nonn

Author

Leroy Quet, Dec 17 2007

Extensions

More terms from Diana L. Mecum, Jul 13 2008

Status

approved