A114813 Indices of Fibonacci numbers with 4 prime factors when counted with multiplicity.

20, 27, 28, 32, 52, 55, 74, 77, 85, 87, 93, 97, 115, 123, 143, 146, 149, 157, 161, 163, 178, 187, 197, 209, 211, 214, 215, 221, 223, 239, 242, 249, 262, 269, 283, 287, 307, 311, 313, 321, 334, 349, 379, 391, 393, 409, 421, 453, 487, 493, 499, 523, 581, 586

Offset

1,1

Comments

1559, 1609, 2131, 2281, 2351, 2459, 2539, 3119, 3371, 4993, 5839, 6217, 7591, 7741, 8353, 9931 are also terms (data from Kelly link). - Chai Wah Wu, Nov 11 2019

Links

Amiram Eldar, Table of n, a(n) for n = 1..86

Blair Kelly, Fibonacci and Lucas Factorizations.

Example

a(1)=20 because 20th Fibonacci number (i.e., 6765) consists of 4 prime factors (i.e., 3*5*11*41).

Mathematica

t = {}; Do[f = FactorInteger[Fibonacci[n]]; If[Total[Transpose[f][[2]]] == 4, AppendTo[t, n]], {n, 2, 100}]; t (* T. D. Noe, Mar 14 2014 *)

Prog

(PARI) n=1; while(n<340, if(bigomega(fibonacci(n))==4, print1(n, ", ")); n++)

Crossrefs

Column k=4 of A303215.

Sequence in context: A219456 A248787 A070717 * A069827 A194674 A059617

Adjacent sequences: A114810 A114811 A114812 * A114814 A114815 A114816

Keyword

nonn,changed

Author

Shyam Sunder Gupta, Feb 19 2006

Extensions

More terms from Ryan Propper, May 22 2006

Status

approved