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Numbers k such that 10*k^k - 9 is prime.
4

%I #20 Mar 29 2023 04:53:11

%S 2,4,14,80,1133,4120

%N Numbers k such that 10*k^k - 9 is prime.

%C 10*1133^1133 - 9 is a probable prime.

%C a(6) > 3000. - _Tyler NeSmith_, May 15 2021

%o (PARI) isok(k) = ispseudoprime(10*k^k - 9); \\ _Altug Alkan_, Apr 02 2018

%Y Numbers k such that b*k^k - b + 1 is prime: A110931 (b=2), A302132 (b=3), A301521 (b=4), A302123 (b=6), A302133 (b=8), A302134 (b=9), this sequence (b=10).

%Y Cf. A302137.

%K nonn,more

%O 1,1

%A _Seiichi Manyama_, Apr 02 2018

%E a(6) from _Michael S. Branicky_, Mar 28 2023