A216181 Numbers n such that (11^n - 4^n)/7 is prime.

3, 5, 11, 17, 71, 89, 827, 22307, 45893, 63521

Offset: 1

Author

Robert Price, Mar 11 2013

Keywords

• nonn
• hard
• more

Comments

All terms are prime.

Next term > 10^5.

Crossrefs

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

Programs

Mathematica

Select[Prime[Range[1, 100000]], PrimeQ[(11^# - 4^#)/7]&]

PARI

is(n)=ispseudoprime((11^n-4^n)/7) \\ Charles R Greathouse IV, Feb 20 2017