A231374 Numbers n such that 3^9*2^n - 1 is prime.

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

Author

Lei Zhou, Nov 08 2013

Keywords

• nonn
• hard

Comments

Riesel Primes with k = 3^9 = 19683.

Checked up to n = 1000000.

Examples

			19683*2^4-1=314927 is a prime number.
		

Crossrefs

Cf. A002235, A002236, A050539, A050566, A050880, A230527, A230537, A212311.

Programs

Mathematica

i=0;Table[While[i++;cp=19683*2^i-1;!PrimeQ[cp]];i,{j,1,20}]

PARI

is(n)=ispseudoprime(3^9*2^n-1) \\ Charles R Greathouse IV, Jun 13 2017