A193292 Number of odd divisors of Fibonacci(n).

1, 1, 1, 2, 2, 1, 2, 4, 2, 4, 2, 3, 2, 4, 4, 8, 2, 4, 4, 16, 4, 4, 2, 12, 6, 4, 8, 16, 2, 16, 4, 16, 4, 4, 8, 32, 8, 8, 4, 64, 4, 16, 2, 32, 16, 8, 2, 48, 8, 48, 4, 16, 4, 32, 16, 96, 16, 8, 4, 192, 4, 8, 16, 64, 8, 16, 8, 32, 16, 128, 4, 256, 4, 16, 24, 32

Offset

1,4

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..1000

Formula

a(n) = A001227(A000045(n)). - Michel Marcus, Jan 14 2014

Example

a(16) = 8 because Fibonacci(16) = 987 = 3 * 7 * 47 and the 8 odd divisors are {1, 3, 7, 21, 47, 141, 329, 987}.

Mathematica

f[n_] := Block[{d = Divisors[Fibonacci[n]]}, Count[OddQ[d], True]]; Table[
  f[n], {n, 110}]

Prog

(PARI) a(n)=n=fibonacci(n); numdiv(n>>valuation(n, 2)) \\ Charles R Greathouse IV, Jul 30 2011

Crossrefs

Cf. A000045, A193291.

Sequence in context: A294931 A365402 A336856 * A275297 A353368 A300667

Adjacent sequences: A193289 A193290 A193291 * A193293 A193294 A193295

Keyword

nonn

Author

Michel Lagneau, Jul 21 2011

Status

approved