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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A195155 Number of divisors d of n such that d-1 also divides n or d-1 = 0. 3
 1, 2, 1, 2, 1, 3, 1, 2, 1, 2, 1, 4, 1, 2, 1, 2, 1, 3, 1, 3, 1, 2, 1, 4, 1, 2, 1, 2, 1, 4, 1, 2, 1, 2, 1, 4, 1, 2, 1, 3, 1, 4, 1, 2, 1, 2, 1, 4, 1, 2, 1, 2, 1, 3, 1, 3, 1, 2, 1, 6, 1, 2, 1, 2, 1, 3, 1, 2, 1, 2, 1, 5, 1, 2, 1, 2, 1, 3, 1, 3, 1, 2, 1, 5, 1, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS First differs from A055874 at a(20). LINKS Harvey P. Dale, Table of n, a(n) for n = 1..1000 FORMULA a(n) = A000005(n) - A195150(n). a(n) = 1 + A129308(n). a(2n-1) = 1; a(2n) = 1 + A007862(n). MAPLE with(numtheory): a:= n-> add(`if`(d=1 or irem(n, d-1)=0, 1, 0), d=divisors(n)): seq(a(n), n=1..200); # Alois P. Heinz, Oct 17 2011 MATHEMATICA d1[n_]:=Module[{d=Rest[Divisors[n]]}, Count[d, _?(Divisible[n, #-1]&)]+1]; Array[d1, 90] (* Harvey P. Dale, Oct 31 2013 *) CROSSREFS Cf. A000005, A007862, A049820, A055874, A129308, A137921, A195150, A195153. Sequence in context: A204917 A232098 A055874 * A178544 A161506 A066451 Adjacent sequences: A195152 A195153 A195154 * A195156 A195157 A195158 KEYWORD nonn AUTHOR Omar E. Pol, Sep 19 2011 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.

Last modified November 29 20:12 EST 2023. Contains 367447 sequences. (Running on oeis4.)