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%I #12 Dec 14 2019 08:14:20
%S 0,1,2,3,5,6,7,10,39,99,115,158,697,966,2602,2899,4057,5226,8279,17946
%N Numbers k such that 3*7^k + 2 is prime.
%C a(21) > 20000. - _Jinyuan Wang_, Dec 14 2019
%t Do[ If[ PrimeQ[ 3*7^n + 2 ], Print[n] ], {n, 1, 6000} ]
%o (PARI) is(n)=ispseudoprime(3*7^n+2) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y Cf. A059091 (3*7^k-2 is prime).
%K nonn,more
%O 1,3
%A _Robert G. Wilson v_, Feb 12 2001
%E a(19)-a(20) from _Jinyuan Wang_, Dec 14 2019
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