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A128349 Numbers n such that (13^n - 5^n)/8 is prime. 18
5, 19, 71, 197, 659, 22079, 61949 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All terms are primes.

a(8) > 10^5. - Robert Price, Mar 05 2013

LINKS

Table of n, a(n) for n=1..7.

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)/8) \\ Charles R Greathouse IV, Feb 17 2017

CROSSREFS

Cf. A062572, A128344, A128345, A128346, A128347, A128348, A128350, A128351, A128352, A128353, A128354. Cf. A004061, A082182, A121877, A059802. Cf. A057171, A082387, A122853, A128335, A128336, A128337, A128338, A128339, A128340, A128341, A128342.

Sequence in context: A243413 A222538 A095073 * A255449 A296630 A001834

Adjacent sequences:  A128346 A128347 A128348 * A128350 A128351 A128352

KEYWORD

hard,more,nonn

AUTHOR

Alexander Adamchuk, Feb 27 2007

EXTENSIONS

a(6)-a(7) from Robert Price, Mar 05 2013

STATUS

approved

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Last modified June 20 09:12 EDT 2019. Contains 324234 sequences. (Running on oeis4.)