A119588 Numbers n such that the number of divisors of Fibonacci(n), tau(Fibonacci(n)), is not a perfect power of 2.

12, 24, 25, 36, 48, 50, 56, 60, 72, 75, 84, 91, 96, 100, 108, 110, 112, 120, 132, 144, 150, 153, 156, 168, 175, 180, 182, 192, 200, 204, 216, 220, 224, 225, 228, 240, 252, 264, 273, 275, 276, 280, 300, 306, 312, 324, 325, 330, 336, 342, 348, 350, 360, 364, 372

Offset

1,1

Comments

Has many terms in common with A023172 (41 below 1000), but neither is a subsequence of the other since 125 is not in this sequence.

Links

Table of n, a(n) for n=1..55.

Blair Kelly, Fibonacci and Lucas Factorizations.

Formula

a(n) = {k: tau(Fibonacci(k)) != 2^i for all i}.

Example

F(12) = 144 has 15 divisors: {1, 2, 3, 4, 6, 8, 9, 12, 16, 18, 24, 36, 48, 72, 144}. Since 15 is not a power of 2, 12 is in the sequence.
F(24) = 46368 has 72 divisors. Since 72 is not a power of 2, 24 is in the sequence.

Mathematica

Do[If[ !IntegerQ[Log[2, DivisorSigma[0, Fibonacci[n]]]], Print[n]], {n, 10^3}]

Crossrefs

Sequence in context: A296749 A297276 A095780 * A167994 A065303 A239673

Adjacent sequences: A119585 A119586 A119587 * A119589 A119590 A119591

Keyword

nonn

Author

Ryan Propper, Jun 01 2006

Status

approved