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%I #17 Jul 09 2024 08:53:31
%S 0,1,2,5,11,30,57,78,91,390,462,667,1214,1811,2054,2937,3055,8518,
%T 10665,25430,45910
%N Numbers k such that 2*7^k + 3 is prime.
%C a(20) > 21059. - _Jinyuan Wang_, Dec 08 2019
%t Do[ If[ PrimeQ[ 2*7^n + 3 ], Print[n] ], {n, 1, 6000} ]
%o (PARI) is(n)=ispseudoprime(2*7^n+3) \\ _Charles R Greathouse IV_, Jun 13 2017
%K nonn,more,changed
%O 1,3
%A _Robert G. Wilson v_, Feb 12 2001
%E a(18)-a(19) from _Jinyuan Wang_, Dec 08 2019
%E a(20)-a(21) from _Michael S. Branicky_, Jul 09 2024
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