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%I #22 Jul 24 2025 03:26:44
%S 2,6,10,26,42,58,68,196,266,602,1170,1288,1290,2990,4110,6292,7446,
%T 36928,57490,65478,78570,188832,273452
%N Numbers k such that 8^k + 7 is prime.
%C All terms are equal to 1/3 of the multiples of 3 in A057195.
%C Naturally these numbers are even because (9-1)^(2n+1)+7 is divisible by 3. - _Bruno Berselli_, Oct 03 2012
%t Select[Range[10000], PrimeQ[8^# + 7] &]
%o (PARI) is(n)=ispseudoprime(8^n+7) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y Cf. A057195, A217354, A217355.
%Y Cf. A144360 (associated primes).
%K nonn,more
%O 1,1
%A _Vincenzo Librandi_, Oct 02 2012
%E a(18)-a(22) from A057195 by _Robert Price_, Jul 23 2017
%E a(23) from the data at A057195 added by _Amiram Eldar_, Jul 23 2025