%I #33 Sep 15 2024 01:58:50

%S 2,4,8,14,42,420,1344

%N Numbers k such that 29^k - 2 is prime.

%C a(8) > 10^4, if it exists. - _Amiram Eldar_, Mar 10 2023

%C All terms in this sequence are even. - _Yifan Xie_, Mar 12 2023

%C a(8) > 5*10^4, if it exists. - _Michael S. Branicky_, Sep 14 2024

%e 4 is a term because 29^4 - 2 = 707279 is a prime number.

%t Select[Range[1400], PrimeQ[29^# - 2] &] (* _Amiram Eldar_, Mar 10 2023 *)

%o (PARI) is(k) = isprime(29^k - 2);

%Y Cf. A087886 (29^k + 2 is prime).

%Y Cf. A128460, A128459, A128457, A109076, A090669, A105772, A109080, (and similar others).

%K nonn,more

%O 1,1

%A _Arsen Vardanyan_, Mar 07 2023