A102657 - OEIS

%I #26 Sep 17 2024 15:10:32

%S 1,2,5,6,7,9,11,13,14,20,23,25,26,27,28,32,33,36,37,40,42,48,49,50,51,

%T 58,61,62,68,74,75,76,77,78,81,84,92,96,103,104,109,111,119,120,126,

%U 127,133,135,137,141,142,144,145,149,153,156,158,163,166,168,169,172,176

%N Numbers k such that 11*k^2 + 11*k + 1 is prime.

%e For k=1,  11*k^2 + 11*k + 1 = 11*1^2  + 11*1  + 1 = 23 (prime).

%e For k=20, 11*k^2 + 11*k + 1 = 11*20^2 + 11*20 + 1 = 4621 (prime).

%e For k=40, 11*k^2 + 11*k + 1 = 11*40^2 + 11*40 + 1 = 18041 (prime).

%t Select[Range[200],PrimeQ[11#^2+11#+1]&] (* _Harvey P. Dale_, Aug 15 2012 *)

%o (Magma) [n: n in [0..1000] | IsPrime(11*n^2+11*n+1)]; // _Vincenzo Librandi_, Nov 17 2010

%o (PARI) is(n)=isprime(11*n^2+11*n+1) \\ _Charles R Greathouse IV_, Jun 13 2017

%K nonn,easy

%O 1,2

%A _Parthasarathy Nambi_, Feb 02 2005