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A118305
Numbers k such that 3*k^k-1 is prime.
0
1, 2, 6, 16, 5436, 6238
OFFSET
1,2
COMMENTS
Six terms found and primes proved by PrimeForm ([N+1, Brillhart-Lehmer-Selfridge]). 3*6238^6238-1 has 23674 digits. No more terms <= 8800.
No more terms <= 25000. - Michael S. Branicky, Oct 13 2024
PROG
(PARI) is(n)=ispseudoprime(3*n^n-1) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
Sequence in context: A144690 A317351 A296108 * A139629 A057497 A063627
KEYWORD
hard,more,nonn
AUTHOR
Rick L. Shepherd, Apr 22 2006
STATUS
approved