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%I #31 Jan 16 2023 21:40:55
%S 2,3,4,5,7,13,16,23,32,43,64,281,359,487,577,1579,1663,1741,3191,9209,
%T 11257,12743,13093,17027,26633,104243,134227,152287,700897,1205459
%N Numbers k such that (3^k + 1)/(3 - (-1)^k) is a prime.
%p A275575:=n->`if`(isprime((3^n + 1)/(3 - (-1)^n)), n, NULL): seq(A275575(n), n=1..2*10^3); # _Wesley Ivan Hurt_, Dec 26 2016
%t Select[Range[0, 10^3], PrimeQ[(3^# + 1)/(3 - (-1)^#)] &]
%o (PARI) isok(n) = isprime( (3^n + 1)/(3 - (-1)^n)); \\ _Michel Marcus_, Dec 26 2016
%Y Cf. A007658, A171381, A280083.
%K nonn,more
%O 1,1
%A _Thomas Ordowski_, Dec 25 2016