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A128337 Numbers k such that (7^k + 5^k)/12 is prime. 19
11, 31, 173, 271, 547, 1823, 2111, 5519, 7793, 22963, 41077, 49739 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All terms are primes.

a(13) > 10^5. - Robert Price, Nov 20 2012

LINKS

Table of n, a(n) for n=1..12.

MATHEMATICA

k=7; Do[p=Prime[n]; f=(k^p+5^p)/(k+5); If[ PrimeQ[f], Print[p] ], {n, 1, 100}]

PROG

(PARI) is(n)=isprime((7^n+5^n)/12) \\ Charles R Greathouse IV, Feb 17 2017

CROSSREFS

Cf. A057171, A082387, A122853, A128335, A128336, A128338, A128339, A128340, A128341, A128342, A128343.

Cf. A004061, A082182, A121877, A059802.

Cf. A062572, A128344, A128345, A128346, A128347, A128348, A128349, A128350, A128351, A128352, A128353, A128354.

Sequence in context: A001604 A144727 A002535 * A093382 A098264 A023279

Adjacent sequences:  A128334 A128335 A128336 * A128338 A128339 A128340

KEYWORD

hard,more,nonn

AUTHOR

Alexander Adamchuk, Feb 27 2007

EXTENSIONS

a(6)-a(12) from Robert Price, Nov 20 2012

STATUS

approved

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Last modified July 24 14:51 EDT 2021. Contains 346273 sequences. (Running on oeis4.)