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A213073
Numbers n such that (7^n - 4^n)/3 is prime.
1
2, 5, 11, 61, 619, 2879, 2957, 24371, 69247, 376463, 571199, 624803
OFFSET
1,1
COMMENTS
All terms are primes.
Next term > 10^6.
LINKS
Jon Grantham and Andrew Granville, Fibonacci primes, primes of the form 2^n-k and beyond, arXiv:2307.07894 [math.NT], 2023.
MATHEMATICA
k=7; Do[p=Prime[n]; f=(k^p-4^p)/(k-4); If[ PrimeQ[f], Print[p] ], {n, 1, 100}]
PROG
(PARI) is(n)=ispseudoprime((7^n-4^n)/3) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
KEYWORD
hard,more,nonn
AUTHOR
Robert Price, Jun 04 2012
EXTENSIONS
a(10)-a(12) from Jon Grantham, Jul 29 2023
STATUS
approved