A193291 -id:A193291 - cp's OEIS frontend

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

Michel Lagneau, Jul 21 2011

nonn

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

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

Cf. A000045, A193291.

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

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

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

A193294 Sum of even divisors of Fibonacci(n).

Original entry on oeis.org

0, 0, 2, 0, 0, 14, 0, 0, 36, 0, 0, 390, 0, 0, 744, 0, 0, 5040, 0, 0, 11816, 0, 0, 154752, 0, 0, 213840, 0, 0, 1999872, 0, 0, 3564360, 0, 0, 46656000, 0, 0, 63517896, 0, 0, 526048320, 0, 0, 1465647264, 0, 0, 16665772032, 0, 0, 20377766312, 0, 0, 173039328000

Offset: 1

Michel Lagneau, Jul 21 2011

nonn

			a(6) = 14 because Fibonacci(6) = 8, and the sum of the even divisors {2, 4, 8} = 14.

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

Cf. A000045, A193291.

Table[Total[Select[Divisors[Fibonacci[n]], EvenQ[ # ]&]], {n, 75}]

a(n)=if(n%3,0,2*sigma(fibonacci(n)/2)) \\ Charles R Greathouse IV, Jul 31 2011

cp's OEIS Frontend

A193292 Number of odd divisors of Fibonacci(n).

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