A128032 Numbers k such that (19^k - 3^k)/16 is prime.

73, 271, 421, 2711

Offset: 1

Author

Alexander Adamchuk, Feb 11 2007

Keywords

• hard
• more
• nonn

Comments

All terms are primes.

No other terms <= 10^5. - Robert Price, Aug 27 2011

Crossrefs

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

Programs

Mathematica

k=16; Select[ Prime[ Range[1,200] ], PrimeQ[ ((k+3)^# - 3^#)/k ]& ]

PARI

is(n)=isprime((19^n-3^n)/16) \\ Charles R Greathouse IV, Feb 17 2017

Extensions

2711 from Farideh Firoozbakht, Apr 07 2007