A084125 - OEIS

%I #18 Dec 07 2024 02:24:51

%S 1,3,6,7,11,29,106,111,138,966,1203,2719,3357,11445,15066,16837,36750,

%T 77439,80133

%N Numbers k such that 13*3^k + 2 is prime.

%C Values corresponding to 29, 106, 111, 138, 966, 1203 and 2719 (1299 digits) have been certified prime with Primo. 13*3^3357 + 2 is a probable prime. There are no other terms <= 6000.

%C No more terms below 50000. - _Amiram Eldar_, Sep 11 2019

%C No more terms below 100000. - _Michael S. Branicky_, Dec 06 2024

%e Primes 41,353,9479,28433 are 13*3^1+2, 13*3^3+2, 13*3^6+2, 13*3^7+2.

%t Select[Range[1000], PrimeQ[13 * 3^# + 2] &] (* _Amiram Eldar_, Sep 11 2019 *)

%o (PARI) for(n=1,6000,if(isprime(13*3^n+2),print1(n,",")))

%Y Cf. A084124.

%K nonn,more

%O 1,2

%A _Rick L. Shepherd_, May 21 2003

%E a(14) (a pseudoprime) from Huseyin Azoguz (huseyin(AT)mmnetz.de), Nov 30 2008

%E a(15)-a(17) from _Amiram Eldar_, Sep 11 2019

%E a(18)-a(19) from _Michael S. Branicky_, Dec 06 2024