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A114812
Indices of Fibonacci numbers with 3 prime factors when counted with multiplicity.
2
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
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
Column k=3 of A303215.
Sequence in context: A199094 A009579 A358760 * A158338 A373257 A351472
KEYWORD
nonn
AUTHOR
Shyam Sunder Gupta, Feb 19 2006
EXTENSIONS
More terms from Ryan Propper, May 22 2006
STATUS
approved