A265121 Integers k such that k*3^k + 2 is prime.

0, 1, 3, 5, 11, 15, 17, 153, 169, 273, 317, 373, 923, 1403, 1969, 2349, 7809, 10313, 12291, 24865, 41289

Offset: 1

Author

Altug Alkan, Dec 01 2015

Keywords

• nonn
• hard
• more

Comments

Initial corresponding primes are 2, 5, 83 and 1217.

How do this sequence and A006552 compare asymptotically?

a(22) > 10^5. - Michael S. Branicky, Oct 08 2024

Examples

			a(3) = 3 because 3^3 * 3 + 2 = 83 is prime.
		

Crossrefs

Cf. A006552, A036290, A182373.

Programs

Magma

[n: n in [0..400] | IsPrime(n*3^n+2)]; // Vincenzo Librandi, Dec 02 2015

Mathematica

Select[Range[0, 10000], PrimeQ[# 3^# + 2] &] (* Vincenzo Librandi, Dec 02 2015 *)

PARI

for(n=0, 1e6, if(ispseudoprime(3^n*n + 2), print1(n, ", ")));

Extensions

a(1) = 0 added by Vincenzo Librandi, Dec 02 2015

a(21) from Michael S. Branicky, May 16 2023