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Integers n such that either 2^n * prime(n) + 3 or 2^n * prime(n) - 3 is prime.
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%I #20 Dec 02 2015 12:32:59

%S 1,3,4,5,6,7,8,9,12,17,18,19,21,23,25,33,34,37,39,41,46,52,55,58,60,

%T 66,91,126,158,191,222,444,529,590,649,751,925,1082,1313,2094,2269,

%U 2424,2572,2923,3732,4009,4172,4207,4521,4866,5125,5617,8583,9032,16235,18492

%N Integers n such that either 2^n * prime(n) + 3 or 2^n * prime(n) - 3 is prime.

%e 1 is a term because 2^1 * 2 + 3 = 7 is prime.

%e 4 is a term because 2^4 * 7 - 3 = 109 is prime.

%t Select[Range@ 5000, Or[PrimeQ[2^# Prime@ # + 3], PrimeQ[2^# Prime@ # - 3]] &] (* _Michael De Vlieger_, Dec 02 2015 *)

%o (PARI) for(n=1, 1e4, if(ispseudoprime(2^n*prime(n) - 3) || ispseudoprime(2^n*prime(n) + 3), print1(n, ", ")));

%Y Cf. A000040, A000079, A239741, A239742.

%K nonn

%O 1,2

%A _Altug Alkan_, Dec 02 2015