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A128030
Numbers k such that (16^k - 3^k)/13 is prime.
28
2, 3, 31, 467, 1747, 29683
OFFSET
1,1
COMMENTS
All terms are primes.
No other terms < 100000.
MATHEMATICA
k=13; Select[ Prime[ Range[1, 200] ], PrimeQ[ ((k+3)^# - 3^#)/k ]& ]
PROG
(PARI) is(n)=isprime((16^n-3^n)/13) \\ Charles R Greathouse IV, Feb 17 2017
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, A128031, A128032.
Sequence in context: A049065 A274609 A372142 * A239593 A214658 A334489
KEYWORD
hard,more,nonn
AUTHOR
Alexander Adamchuk, Feb 11 2007
EXTENSIONS
1747 from Farideh Firoozbakht, Apr 08 2007
a(6)=29683 from Robert Price, Sep 13 2011
STATUS
approved