A217131 Numbers n such that 7^n - 8 is prime.

2, 4, 8, 10, 50, 106, 182, 293, 964, 1108, 1654, 1756, 4601, 8870, 15100, 17446, 22742, 34570, 50150, 95276

Offset: 1

Author

Vincenzo Librandi, Oct 01 2012

Keywords

• nonn

Comments

a(21) > 10^5. - Robert Price, Jan 23 2014

Crossrefs

Cf. A236371, A217131, A191469, A090669, A096305, A217130, A217132, A152213.

Programs

Mathematica

Select[Range[1, 5000], PrimeQ[7^#  - 8] &]

PARI

for(n=1, 5*10^3, if(isprime(7^n-8), print1(n, ", ")))

Extensions

a(14)-a(20) from Robert Price, Jan 23 2014