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A231374
Numbers n such that 3^9*2^n - 1 is prime.
0
4, 7, 19, 22, 32, 46, 50, 62, 83, 103, 124, 142, 190, 230, 256, 260, 422, 596, 1084, 2270, 2770, 5366, 5434, 5762, 6826, 9239, 15211, 22556, 58790, 81319, 172510, 225350, 236326, 258592, 445364, 975020
OFFSET
1,1
COMMENTS
Riesel Primes with k = 3^9 = 19683.
Checked up to n = 1000000.
EXAMPLE
19683*2^4-1=314927 is a prime number.
MATHEMATICA
i=0; Table[While[i++; cp=19683*2^i-1; !PrimeQ[cp]]; i, {j, 1, 20}]
PROG
(PARI) is(n)=ispseudoprime(3^9*2^n-1) \\ Charles R Greathouse IV, Jun 13 2017
KEYWORD
nonn,hard
AUTHOR
Lei Zhou, Nov 08 2013
STATUS
approved