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%I #9 Jan 29 2020 02:51:40
%S 1,3,5,15,21,27,65,191,327,371,575,1895,2375,2607,9735
%N Numbers k such that (7*3^k + 5)/2 is prime.
%C a(16) > 20055. - _Jinyuan Wang_, Jan 29 2020
%t Do[ If[ PrimeQ[ (7*3^n + 5)/2 ], Print[n] ], {n, 0, 5300} ]
%o (PARI) is(n)=ispseudoprime((7*3^n+5)/2) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y Cf. A059569 ((7*3^k-5)/2 is prime).
%K nonn,more
%O 1,2
%A _Robert G. Wilson v_, Feb 16 2001
%E a(15) from _Jinyuan Wang_, Jan 29 2020
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