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Numbers k such that k^2 +-7 are primes.
5

%I #7 Feb 27 2020 12:20:06

%S 6,12,18,36,48,60,66,132,138,162,186,192,216,228,270,330,360,366,408,

%T 468,474,582,606,642,678,708,744,792,1086,1182,1236,1308,1326,1458,

%U 1524,1686,1782,1902,1998,2040,2124,2178,2208,2244,2358,2370,2634,2658,2760

%N Numbers k such that k^2 +-7 are primes.

%H Daniel Starodubtsev, <a href="/A176682/b176682.txt">Table of n, a(n) for n = 1..10000</a>

%e 12 is in the sequence, because 12^2 - 7 = 137 and 12^2 + 7 = 151 are primes.

%t Select[Range[8! ],PrimeQ[ #^2-7]&&PrimeQ[ #^2+7]&]

%Y Cf. A097698, A108701, A176681

%K nonn

%O 1,1

%A _Vladimir Joseph Stephan Orlovsky_, Apr 23 2010