A136165 a(n) = the number of divisors of n that are each not noncoprime to either the previous or the following divisor of n.

1, 2, 2, 1, 2, 2, 2, 1, 1, 2, 2, 3, 2, 2, 2, 1, 2, 2, 2, 1, 2, 2, 2, 3, 1, 2, 1, 1, 2, 4, 2, 1, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 1, 3, 2, 2, 3, 1, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 5, 2, 2, 3, 1, 2, 2, 2, 1, 2, 4, 2, 3, 2, 2, 2, 1, 2, 2, 2, 2, 1, 2, 2, 4, 2, 2, 2, 1, 2, 4, 2, 1, 2, 2, 2, 3, 2, 2, 1, 1, 2, 2, 2, 1, 4

Offset

1,2

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. But 2 and 4 are adjacent divisors which are not coprime. And 7 is next to 14 among divisors of 28 and 7 and 14 are not coprime. Therefore there is a(28) = 1 divisor (1) that is not next to another divisor that it is not coprime to.

Crossrefs

Cf. A136164, A136166, A136167.

Sequence in context: A230594 A072463 A128853 * A134193 A230259 A085030

Adjacent sequences: A136162 A136163 A136164 * A136166 A136167 A136168

Keyword

nonn

Author

Leroy Quet, Dec 17 2007

Extensions

More terms from Diana L. Mecum, Jul 11 2007

Status

approved