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A128346 Numbers n such that (9^n - 5^n)/4 is prime. 18
3, 11, 17, 173, 839, 971 (list; graph; refs; listen; history; internal format)
OFFSET

1,1

COMMENTS

All terms are primes.

MATHEMATICA

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

CROSSREFS

Cf. A062572, A128344, A128345, A128347, A128348, A128349, 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: A124787 A080306 A036448 * A128031 A194128 A127995

Adjacent sequences:  A128343 A128344 A128345 * A128347 A128348 A128349

KEYWORD

hard,more,nonn

AUTHOR

Alexander Adamchuk (alex(AT)kolmogorov.com), Feb 27 2007

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Last modified February 14 22:58 EST 2012. Contains 205685 sequences.