login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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
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
Sequence in context: A169611 A242460 A144494 * A259525 A319071 A316432
KEYWORD
nonn
AUTHOR
Leroy Quet, Dec 17 2007
EXTENSIONS
More terms from Diana L. Mecum, Jul 13 2008
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 12:26 EDT 2024. Contains 371254 sequences. (Running on oeis4.)