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A118305 Numbers n such that 3*n^n-1 is prime. 0
1, 2, 6, 16, 5436, 6238 (list; graph; refs; listen; history; text; internal format)
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

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Last modified August 21 06:54 EDT 2019. Contains 326162 sequences. (Running on oeis4.)