A090206 Nonprime Fibonacci numbers.

0, 1, 1, 8, 21, 34, 55, 144, 377, 610, 987, 2584, 4181, 6765, 10946, 17711, 46368, 75025, 121393, 196418, 317811, 832040, 1346269, 2178309, 3524578, 5702887, 9227465, 14930352, 24157817, 39088169

Offset: 1

Author

Felix Tubiana, Jan 22 2004

Keywords

• easy
• nonn

Comments

It is possible to find a run of at least length n (not necessarily exactly n) such that n consecutive terms in this sequence are also consecutive in the sequence of Fibonacci numbers. However, it is not possible for such a run to be of exactly length n if n is even. - Alonso del Arte, Nov 23 2010

Some terms of this sequence have prime indices in the sequence of Fibonacci numbers (A000045), see A050937. - Alonso del Arte, Aug 16 2013

Examples

			34 is in the sequence as it is a Fibonacci number and it is composite, the product of 2 and 17.
55 is in the sequence as it is a Fibonacci number and it is composite, the product of 5 and 11.
89 is not in the sequence because, although it is a Fibonacci number, it is prime.
		

Crossrefs

Cf. A000045, A005478, A050937, A182602.

Programs

Mathematica

Select[Fibonacci[Range[0, 50]], !PrimeQ[#] &] (* Vladimir Joseph Stephan Orlovsky, Jul 22 2008 *)