A180422 Largest prime immediately preceding a Fibonacci number.

2, 3, 7, 11, 19, 31, 53, 83, 139, 229, 373, 607, 983, 1583, 2579, 4177, 6763, 10939, 17707, 28649, 46351, 75017, 121379, 196387, 317797, 514219, 832003, 1346249, 2178283, 3524569, 5702867, 9227443, 14930341, 24157811, 39088157, 63245971

Offset: 4

Author

Carmine Suriano, Sep 03 2010

Keywords

• nonn

Comments

Limit ratio of two consecutive elements of this sequence is phi=1.61803... the golden ratio.

Examples

			a(7)=53 that is the prime number preceding 55=fib(10).
fib(1)=1, fib(2)=1 and fib(3)=2 are not accounted.
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 4..1000

Crossrefs

Cf. A138184, A000045

Programs

Mathematica

NextPrime[#,-1]&/@Fibonacci[Range[4,40]] (* Harvey P. Dale, Oct 31 2013 *)

PARI

a(n)=precprime(fibonacci(n)-1)

Extensions

Program and cross-ref from Charles R Greathouse IV, Sep 08 2010