A222265 Numbers n such that (13^n + 2^n)/15 is prime.

7, 31, 103, 223, 503, 1171, 1973, 4111, 4729

Offset: 1

Author

Robert Price, May 05 2013

Keywords

• nonn
• hard
• more

Comments

All terms are prime.

a(10) > 10^5.

Crossrefs

Cf. A125956, A125957, A057159, A128071, A213176.

Programs

Mathematica

Select[Prime[Range[1, 100000]], PrimeQ[(13^# + 2^#)/15]&]

PARI

forprime(p=3,10^6, if(ispseudoprime((13^p + 2^p)/15), print1(p,", ") ) ); \\ Joerg Arndt, Jul 29 2013

Extensions

Removed incorrect first term of "2".