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

1,1

Comments

Riesel Primes with k = 3^9 = 19683.

Checked up to n = 1000000.

Links

Table of n, a(n) for n=1..36.

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

Crossrefs

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

Sequence in context: A132207 A097537 A032723 * A173017 A063605 A024824

Adjacent sequences: A231371 A231372 A231373 * A231375 A231376 A231377

Keyword

nonn,hard

Author

Lei Zhou, Nov 08 2013

Status

approved