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Value of C in y = x^2 + 5x + C such that y is prime for all x = 0 to 3.
1

%I #9 Aug 09 2013 15:49:12

%S 5,17,23,47,83,167,227,257,443,563,593,677,1277,1283,1613,1973,2333,

%T 2837,2903,3533,5393,5843,6197,6263,6977,7523,8087,8363,11807,12473,

%U 12893,13463,13907,14537,14717,15077,15263,15377,17093,17327,19913

%N Value of C in y = x^2 + 5x + C such that y is prime for all x = 0 to 3.

%e a(2) = 17: y = x^2+5x+17.

%e If x = 0; y = 0+0+17 = 17, which is prime.

%e If x = 1; y = 1+5+17 = 23, which is prime.

%e If x = 2; y = 4+10+17 = 31, which is prime.

%e If x = 3; y = 9+15+17 = 41, which is prime.

%o (PARI) isok(n) = {for (x=0, 3, if (! isprime(x^2+5*x+n), return (0));); return (1);} \\ _Michel Marcus_, Aug 09 2013

%K nonn

%O 1,1

%A _Ray G. Opao_, Aug 22 2004