A114812 Indices of Fibonacci numbers with 3 prime factors when counted with multiplicity.

6, 15, 16, 21, 25, 33, 35, 37, 38, 39, 46, 49, 51, 58, 62, 65, 67, 82, 86, 103, 106, 119, 122, 139, 142, 145, 158, 166, 179, 181, 226, 233, 235, 241, 257, 263, 274, 281, 299, 301, 317, 337, 383, 389, 419, 457, 463, 473, 479, 491, 521, 541, 557, 619, 643, 659

Offset

1,1

Comments

1811, 1933, 1997, 2069, 2087, 2203, 2221, 2311, 2663, 2713, 3631, 4157, 4651, 5107, 6701, 7211, 8123 are also terms (from data in Kelly link). - Chai Wah Wu, Nov 11 2019

Links

Amiram Eldar, Table of n, a(n) for n = 1..83

Blair Kelly, Fibonacci and Lucas Factorizations.

Formula

{n: A038575(n)=3}. [R. J. Mathar, Jun 08 2010]

Example

a(2)=15 because 15th fibonacci number(i.e. 610) consists of 3 prime factors (i.e. 2*5*61)

Mathematica

t = {}; Do[f = FactorInteger[Fibonacci[n]]; If[Total[Transpose[f][[2]]] == 3, AppendTo[t, n]], {n, 2, 100}]; t (* T. D. Noe, Mar 14 2014 *)
Flatten[Position[Fibonacci[Range[700]], _?(PrimeOmega[#]==3&)]] (* Harvey P. Dale, Feb 15 2015 *)

Prog

(PARI) n=1; while(n<340, if(bigomega(fibonacci(n))==3, print1(n, ", ")); n++)

Crossrefs

Cf. A072381, A114813.

Column k=3 of A303215.

Sequence in context: A199094 A009579 A358760 * A158338 A351472 A139204

Adjacent sequences: A114809 A114810 A114811 * A114813 A114814 A114815

Keyword

nonn

Author

Shyam Sunder Gupta, Feb 19 2006

Extensions

More terms from Ryan Propper, May 22 2006

Status

approved