A090819 Primes p such that the p-th Fibonacci number is nonprime.

2, 19, 31, 37, 41, 53, 59, 61, 67, 71, 73, 79, 89, 97, 101, 103, 107, 109, 113, 127, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349

Offset: 1

Author

Cino Hilliard, Feb 11 2004

Keywords

• easy
• nonn

Comments

Is it true that a(n) ~ n log n? - Charles R Greathouse IV, Aug 15 2015

Examples

			Fibonacci(37) = 24157817 = 73*149*2221. [corrected by _Bobby Jacobs_, Sep 25 2017]
		

Crossrefs

Cf. A000045, A001605, A134787.

Essentially the same as A038672.

Programs

Mathematica

Select[Prime[Range[62]], ! PrimeQ[Fibonacci[#]] &] (* Jayanta Basu, Jul 10 2013 *)

PARI

f(n) = forprime(x=2,n,p=fibonacci(x);if(!isprime(p),print1(x",")))

Formula

a(n) = prime(A134787(n)). - Amiram Eldar, Oct 25 2024

Extensions

Definition corrected by Don Reble, Sep 04 2008