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n^2 + {1,3,7} are primes.
5

%I #14 May 13 2013 01:54:18

%S 2,4,10,74,146,256,440,470,584,920,1070,1156,1324,1394,1420,2080,2470,

%T 2600,3326,3746,4796,5996,6460,7160,7466,8894,9164,9554,9596,10490,

%U 10970,11204,11246,11336,11374,12314,12386,13394,14290,15586,16250,16330,17060

%N n^2 + {1,3,7} are primes.

%C Under Schinzel's hypothesis H, this sequence is infinite. - _Charles R Greathouse IV_, Apr 23 2012

%H Charles R Greathouse IV, <a href="/A182238/b182238.txt">Table of n, a(n) for n = 1..10000</a>

%e 2^2+{1,3,7}= {5,7,11} all prime, 4^2+{1,3,7}= {17,19,23} all prime.

%o (PARI)

%o { forstep ( n=2, 10^6, 2,

%o ns = n * n;

%o if ( ! isprime( ns+1 ), next() );

%o if ( ! isprime( ns+3 ), next() );

%o if ( ! isprime( ns+7 ), next() );

%o print1(n, ", ");

%o ); }

%o /* _Joerg Arndt_, Apr 22 2012 */

%Y Intersection of A005574, A049422, A114270.

%K nonn

%O 1,1

%A _Zak Seidov_, Apr 20 2012