A128339 - OEIS

A128339

Numbers k such that (9^k + 5^k)/14 is prime.

3, 5, 13, 17, 43, 127, 229, 277, 6043, 11131, 11821

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OFFSET

1,1

COMMENTS

All terms are primes.

a(12) > 10^5. - Robert Price, Dec 26 2012

LINKS

MATHEMATICA

k=9; Do[p=Prime[n]; f=(k^p+5^p)/(k+5); If[ PrimeQ[f], Print[p] ], {n, 1, 100}]

PROG

(PARI) is(n)=isprime((9^n+5^n)/14) \\ Charles R Greathouse IV, Feb 17 2017

(Magma) [n: n in [3..300] |IsPrime((9^n + 5^n) div 14)]; // Vincenzo Librandi, Nov 02 2018

CROSSREFS

KEYWORD

hard,more,nonn

AUTHOR

EXTENSIONS

3 more PRP terms from Sean A. Irvine, Oct 01 2009

STATUS

approved