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A128071
Numbers k such that (3^k + 13^k)/16 is prime.
12
3, 7, 127, 2467, 3121, 34313
OFFSET
1,1
COMMENTS
All terms are primes.
a(4) is certified prime by primo; a(5) is a probable prime. - Ray G. Opao, Aug 02 2007
a(7) > 10^5. - Robert Price, Apr 14 2013
MATHEMATICA
k=13; Do[ p=Prime[n]; f=(3^p+k^p)/(k+3); If[ PrimeQ[f], Print[p]], {n, 1, 100} ]
PROG
(PARI) is(n)=isprime((3^n+13^n)/16) \\ Charles R Greathouse IV, Feb 17 2017
CROSSREFS
Cf. A007658 = numbers n such that (3^n + 1)/4 is prime. Cf. A057469 = numbers n such that (3^n + 2^n)/5 is prime. Cf. A122853 = numbers n such that (3^n + 5^n)/8 is prime. Cf. A128066, A128067, A128068, A128069, A128070, A128072, A128073, A128074, A128075. 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, A128031, A128032.
Sequence in context: A042329 A125956 A260642 * A079622 A182330 A005844
KEYWORD
hard,more,nonn
AUTHOR
Alexander Adamchuk, Feb 14 2007
EXTENSIONS
One more term from Ray G. Opao, Aug 02 2007
a(6) from Robert Price, Apr 14 2013
STATUS
approved