A217133 Numbers n such that 5^n + 8 is prime.

1, 95, 335, 3155, 28651, 91135

Offset: 1

Author

Vincenzo Librandi, Oct 01 2012

Keywords

• nonn
• more

Comments

Naturally these numbers are odd since (6-1)^(2n)+8 is divisible by 3. - Bruno Berselli, Oct 04 2012

a(7) > 10^5. - Robert Price, Feb 03 2014

a(7) > 5*10^5. - Tyler NeSmith, Apr 24 2022

Crossrefs

Cf. A087885, A089142, A124621.

Programs

Mathematica

Select[Range[1, 15000, 2], PrimeQ[5^# + 8] &]

PARI

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

Extensions

a(5)-a(6) from Robert Price, Feb 03 2014