A128031 Numbers k such that (17^k - 3^k)/14 is prime.

3, 11, 17, 491, 23029

Offset: 1

Author

Alexander Adamchuk, Feb 11 2007

Keywords

• hard
• more
• nonn

Comments

All terms are primes.

No other terms < 100000.

Crossrefs

Cf. A028491 = numbers n such that (3^n - 1)/2 is prime.

Cf. A057468 = numbers n such that 3^n - 2^n is prime.

Cf. A059801 = numbers n such that 4^n - 3^n is prime.

Cf. A121877 = numbers n such that (5^n - 3^n)/2 is a prime.

Cf. A128024, A128025, A128026, A128027, A128028, A128029, A128030, A128032.

Programs

Mathematica

k=14; Select[ Prime[ Range[1,200] ], PrimeQ[ ((k+3)^# - 3^#)/k ]& ]

PARI

is(n)=isprime((17^n-3^n)/14) \\ Charles R Greathouse IV, Feb 17 2017

Extensions

a(5)=23029 from Robert Price, Nov 03 2011