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A136166 a(n) = the number of divisors of n that are each not coprime to the previous or the following divisor of n. 6
0, 0, 0, 2, 0, 2, 0, 3, 2, 2, 0, 3, 0, 2, 2, 4, 0, 4, 0, 5, 2, 2, 0, 5, 2, 2, 3, 5, 0, 4, 0, 5, 2, 2, 2, 6, 0, 2, 2, 6, 0, 6, 0, 5, 3, 2, 0, 7, 2, 4, 2, 5, 0, 6, 2, 6, 2, 2, 0, 7, 0, 2, 3, 6, 2, 6, 0, 5, 2, 4, 0, 9, 0, 2, 4, 5, 2, 6, 0, 8, 4, 2, 0, 8, 2, 2, 2, 7, 0, 8, 2, 5, 2, 2, 2, 9, 0, 4, 5, 8, 0, 6, 0, 7, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

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) =5 divisors that are each next to at least one divisor they are not coprime to. (These five divisors are 2,4,7,14,28.)

CROSSREFS

Cf. A136164, A136165, A136167.

Sequence in context: A169611 A242460 A144494 * A259525 A319071 A316432

Adjacent sequences:  A136163 A136164 A136165 * A136167 A136168 A136169

KEYWORD

nonn

AUTHOR

Leroy Quet, Dec 17 2007

EXTENSIONS

More terms from Diana L. Mecum, Jul 13 2008

STATUS

approved

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Last modified May 10 21:08 EDT 2021. Contains 343780 sequences. (Running on oeis4.)