A138859 Smallest prime factor of Fibonacci(3n)-1, i.e., A020639(A000071(3n)).

7, 3, 11, 3, 3, 5, 199, 13, 13, 3, 37, 3, 3, 89, 5, 11, 7, 3, 59, 3, 3, 11, 11, 37, 37, 3, 370248451, 3, 3, 139, 13, 5, 5, 3, 5, 3, 3, 59, 709, 557, 127, 3, 11, 3, 3, 5, 9375829, 73, 7, 3, 29, 3, 3, 2789, 5, 11, 47, 3, 13, 3, 3, 11, 11, 13, 7, 3, 809, 3, 3, 953, 47927441, 5, 5

Offset

2,1

Comments

F(n)-1 is even if n is not a multiple of 3.

Links

Amiram Eldar, Table of n, a(n) for n = 2..934 (terms 2..379 from Chai Wah Wu)

Formula

a(n) = A020639(A000071(3n)).

Mathematica

Table[FactorInteger[Fibonacci[3n]-1][[1, 1]], {n, 2, 80}] (* Harvey P. Dale, Aug 08 2017 *)

Prog

(PARI) A138859(n)=factor(fibonacci(3*n)-1)[1, 1] /* A138859 is defined only for n>1 ! */

Crossrefs

Cf. A000071, A014445, A020639.

Sequence in context: A084000 A168197 A257324 * A257328 A361416 A076569

Adjacent sequences: A138856 A138857 A138858 * A138860 A138861 A138862

Keyword

nonn

Author

M. F. Hasler, Apr 05 2008

Status

approved