A118305 Numbers n such that 3*n^n-1 is prime.

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.

Links

Table of n, a(n) for n=1..6.

Prog

(PARI) is(n)=ispseudoprime(3*n^n-1) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Cf. A118306, A110931.

Sequence in context: A144690 A317351 A296108 * A139629 A057497 A063627

Adjacent sequences: A118302 A118303 A118304 * A118306 A118307 A118308

Keyword

hard,more,nonn

Author

Rick L. Shepherd, Apr 22 2006

Status

approved