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%I #43 Jul 29 2023 20:52:08
%S 0,12,36,48,72,120,605376
%N Numbers k such that 1 + 3^k + 5^k is prime.
%C Next term, if it exists, is greater than 35000. - _Vaclav Kotesovec_, Jan 26 2016
%C No more terms up to 75000 (previous range rechecked). All terms are multiples of 12: if k > 0 is not a multiple of 12, 1 + 3^k + 5^k is divisible by 3, 5 or 7. - _Rick L. Shepherd_, Aug 06 2017
%C Next term, if it exists, is greater than 10^6. - _Jon Grantham_, Jul 29 2023
%p A076515:=n->`if`(isprime(1+3^n+5^n), n, NULL): seq(A076515(n), n=0..200); # _Wesley Ivan Hurt_, Aug 06 2017
%t Do[ If[ PrimeQ[1 + 3^n + 5^n], Print[n]], {n, 0, 3500, 2}]
%t Select[Range[0,5000],PrimeQ[1+3^#+5^#]&] (* _Harvey P. Dale_, Mar 09 2012 *)
%o (Magma) [n: n in [0..1000]|IsPrime(3^n+5^n+1)] // _Vincenzo Librandi_, Jan 22 2011
%o (PARI) lista(nn) = for(n=0, nn, if(ispseudoprime(1 + 3^n + 5^n), print1(n, ", "))); \\ _Altug Alkan_, Jan 25 2016
%Y Cf. A008594, A074507, A268064, A268065, A268067.
%K nonn,more
%O 1,2
%A _Zak Seidov_, Oct 17 2002
%E a(7) from _Jon Grantham_, Jul 29 2023
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