A124067 Numbers k such that 2*F(k) + 1 is a prime, where F = A000045.

1, 2, 3, 4, 5, 6, 8, 11, 13, 19, 21, 22, 24, 27, 40, 44, 51, 62, 92, 139, 208, 224, 293, 307, 421, 509, 741, 861, 966, 989, 1046, 1100, 1102, 1109, 1182, 1547, 1766, 1813, 2048, 2720, 2726, 6012, 6790, 7132, 8301, 8699, 10062, 11102, 15827, 23918, 26747, 29389, 37229, 38211, 68726

Offset: 1

Author

Giovanni Teofilatto, Dec 12 2006

Keywords

• nonn

Crossrefs

Cf. A000045, A001588, A124081 (associated primes).

Programs

Magma

[n: n in [1..1200] | IsPrime(2*Fibonacci(n)+1)]; // Vincenzo Librandi, Aug 13 2013

Mathematica

Select[Range[10000], PrimeQ[2 Fibonacci[#] + 1]&] (* Vincenzo Librandi, Aug 13 2013 *)

PARI

isok(n) = isprime(2*fibonacci(n)+1) \\ Michel Marcus, Jun 03 2013

PARI

for(n=1,10^9,if(ispseudoprime(2*fibonacci(n)+1),print1(n,", "))); \\ Joerg Arndt, Aug 13 2013

Extensions

Inserted a(1)=1 and extended by Michel Marcus, Jun 03 2013

More terms from Vincenzo Librandi, Aug 13 2013

a(48) from Jorge Coveiro, Sep 05 2022

a(49)-a(55) from Michael S. Branicky, Jun 17 2023