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%I #41 Sep 05 2024 10:16:22
%S 0,5,14,77,104,2603,2657,24029
%N Numbers k such that 9*10^(2*k) + 3*10^k + 1 is prime.
%e 13 is prime ==> a(1) = 0.
%e 931 = 7^2 * 19.
%e 90301 = 73 * 1237.
%e 9003001 = 7 * 757 * 1699.
%e 900030001 = 13 * 4969 * 13933.
%e 90000300001 is prime ==> a(2) = 5.
%o (PARI) for(k=0, 1e3, if(ispseudoprime(9*100^k+3*10^k+1), print1(k", ")))
%Y Cf. A309738, A309743.
%K nonn,base,more
%O 1,2
%A _Seiichi Manyama_, Aug 15 2019
%E a(8) from _Michael S. Branicky_, Sep 05 2024