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A128342 Numbers k such that (13^k + 5^k)/18 is prime. 23
13, 19, 31, 359, 487, 757, 761, 1667, 2551, 3167, 6829 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All terms are primes.

No other terms below 23600. - Max Alekseyev, Feb 01 2010

a(12) > 10^5. - Robert Price, Apr 30 2013

LINKS

Table of n, a(n) for n=1..11.

MATHEMATICA

k=13; Do[p=Prime[n]; f=(k^p+5^p)/(k+5); If[ PrimeQ[f], Print[p] ], {n, 1, 100}]

PROG

(PARI) is(n)=isprime((13^n+5^n)/18) \\ Charles R Greathouse IV, Feb 17 2017

CROSSREFS

Cf. A057171, A082387, A122853, A128335, A128336, A128337, A128338, A128339, A128340, A128341, A128343. Cf. A004061, A082182, A121877, A059802. Cf. A062572, A128344, A128345, A128346, A128347, A128348, A128349, A128350, A128351, A128352, A128353, A128354.

Sequence in context: A023252 A279426 A241120 * A154076 A275660 A088186

Adjacent sequences:  A128339 A128340 A128341 * A128343 A128344 A128345

KEYWORD

hard,more,nonn

AUTHOR

Alexander Adamchuk, Feb 27 2007

EXTENSIONS

Four more terms from Max Alekseyev, Feb 01 2010

STATUS

approved

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Last modified June 26 04:11 EDT 2019. Contains 324369 sequences. (Running on oeis4.)