A266694 Numbers n such that 2*n*3^n + 1 is prime.

1, 2, 3, 14, 19, 21, 27, 33, 46, 70, 80, 441, 540, 567, 625, 1057, 1119, 1213, 1542, 4263, 4419, 4507, 5186, 7345, 8626, 8853, 11256, 12885, 14688, 15236, 17697, 26770, 57801, 71665

Offset: 1

Author

Juri-Stepan Gerasimov, Jan 02 2016

Keywords

• nonn
• more

Comments

Primes: 2, 3, 19, 1213, 4507, ...

No further terms < 10^5. - Ray Chandler, Apr 13 2016

Examples

			1 is in this sequence because 2*1*3^1 + 1 = 7 is prime.
		

Crossrefs

Cf. A006552.

Programs

Magma

[n: n in [1..2000]| IsPrime(2*n*3^n+1)]; // Vincenzo Librandi, Jan 03 2016

Mathematica

Select[Range[1600], PrimeQ[2 # 3^# + 1] &] (* Vincenzo Librandi, Jan 03 2016 *)

PARI

is(n)=ispseudoprime(2*n*3^n+1) \\ Charles R Greathouse IV, Feb 08 2016

Extensions

a(24) and a(26) inserted by Charles R Greathouse IV, Feb 08 2016

a(28)-a(30) from Charles R Greathouse IV, Feb 08 2016

a(31)-a(32) from Ray Chandler, Apr 05 2016

a(33) from Ray Chandler, Apr 08 2016

a(34) from Ray Chandler, Apr 09 2016