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A128073
Numbers k such that (3^k + 16^k)/19 is prime.
10
5, 17, 61, 673, 919, 2089, 86939
OFFSET
1,1
COMMENTS
All terms are primes.
a(8) > 10^5 - Robert Price, Jun 29 2013
MATHEMATICA
k=16; 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+16^n)/19) \\ Charles R Greathouse IV, Feb 17 2017
CROSSREFS
Cf. A007658 (numbers k such that (3^k + 1)/4 is prime).
Cf. A057469 (numbers k such that (3^k + 2^k)/5 is prime).
Cf. A122853 (numbers k such that (3^k + 5^k)/8 is prime).
Cf. A059801 (numbers k such that 4^k - 3^k is prime).
Cf. A121877 (numbers k such that (5^k - 3^k)/2 is prime).
Sequence in context: A273836 A273704 A146444 * A051736 A301560 A099528
KEYWORD
hard,more,nonn
AUTHOR
Alexander Adamchuk, Feb 14 2007
EXTENSIONS
a(5) from Alexander Adamchuk, Feb 14 2007
a(6) and a(7) from Robert Price, Jun 29 2013
STATUS
approved