%I #12 Jan 05 2024 15:58:00
%S 1,15,44,77,141,208,304,1169,3359,5050,22431,34935,92990
%N Numbers k such that (20^k + 1)^2 - 2 is prime.
%C Such primes are sometimes called Kynea primes of base 20.
%H Prime-Wiki, <a href="https://www.rieselprime.de/ziki/Carol-Kynea_prime">Carol-Kynea prime</a>.
%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Near-SquarePrime.html">Near-Square Prime</a>.
%o (PARI) for(k=1,1200,ispseudoprime((20^k+1)^2-2)&&print1(k,", "))
%Y Cf. A091513 (b=2), A100902 (b=6), A100904 (b=10), A364077 (b=12), A100906 (b=14), A364079 (b=18), A100908 (b=22).
%Y Cf. A364080.
%K nonn,hard,more
%O 1,2
%A _Jeppe Stig Nielsen_, Jul 03 2023