A193292 - OEIS

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

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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}]