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%I #12 Jan 05 2024 15:58:05
%S 1,2,53,183,1281,1300,8041,29936,72820
%N Numbers k such that (20^k - 1)^2 - 2 is prime.
%C Such primes are sometimes called Carol 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. A091515 (b=2), A100901 (b=6), A100903 (b=10), A364076 (b=12), A100905 (b=14), A364078 (b=18), A100907 (b=22).
%Y Cf. A364081.
%K nonn,hard,more
%O 1,2
%A _Jeppe Stig Nielsen_, Jul 03 2023
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