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%I #8 Feb 29 2024 06:19:49
%S 1,2,4,8,10,28,1348,1424,12838
%N Numbers k such that (9^k + 9*k)/9 is prime.
%C If it exists, a(10) > 50000.
%o (PARI) is(n) = ispseudoprime(9^(n-1)+n)
%Y Cf. A221911, A226202.
%K nonn,hard,more
%O 1,2
%A _Hugo Pfoertner_, Feb 27 2024