A271428 Values of k such that F(k)*F(k+1)-1 is a prime, where F(k) is the k-th Fibonacci number (A000045).

3, 6, 24, 42, 48, 86, 102, 138, 182, 302, 438, 506, 926, 1266, 3600, 23550, 24122, 42410, 51432, 82290

Offset

1,1

Comments

a(21) > 10^5. - Robert Price, Apr 14 2016

Links

Table of n, a(n) for n=1..20.

Example

6 is in the sequence because F(6)*F(7)-1 = 8*13-1 = 103, which is prime.

Mathematica

Select[Range[5 * 10^3], PrimeQ[Fibonacci@ # Fibonacci[# + 1] - 1] &] (* Michael De Vlieger, Apr 07 2016 *)

Prog

(PARI) L=List(); for(k=1, 1000, if(ispseudoprime(fibonacci(k)*fibonacci(k+1)-1), listput(L, k))); Vec(L)

Crossrefs

Cf. A000045, A271427.

Sequence in context: A129520 A330300 A047167 * A148649 A148650 A148651

Adjacent sequences: A271425 A271426 A271427 * A271429 A271430 A271431

Keyword

nonn,more

Author

Colin Barker, Apr 07 2016

Extensions

a(15) from Michael De Vlieger, Apr 07 2016

a(16)-a(20) from Robert Price, Apr 14 2016

Status

approved