A230139 Numbers n such that (17^n - 4^n)/13 is prime.

3, 5, 7, 11, 31, 101, 887, 4861

Offset: 1

Author

Robert Price, Oct 10 2013

Keywords

• nonn
• hard
• more

Comments

All terms are prime.

a(9) > 10^5.

Crossrefs

Cf. A004063, A028491, A057468, A059801, A121877, A128024, A128025, A128026, A128027, A128028, A128029, A128030, A128031, A128032, A210506, A128347, A128352, A225807.

Programs

Mathematica

Select[Prime[Range[1, 100000]], PrimeQ[(17^# - 4^#)/13]&]

PARI

is(n)=ispseudoprime((17^n-4^n)/13) \\ Charles R Greathouse IV, Jun 13 2017