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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

%I

%S 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,

%T 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,

%U 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

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

%H Diana Mecum, <a href="/A136166/b136166.txt">Table of n, a(n) for n = 1..1000</a>

%e 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.)

%Y Cf. A136164, A136165, A136167.

%K nonn

%O 1,4

%A _Leroy Quet_, Dec 17 2007

%E More terms from _Diana L. Mecum_, Jul 13 2008

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Last modified June 18 16:47 EDT 2021. Contains 345120 sequences. (Running on oeis4.)