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Primes p such that 42 is a square mod p.
2

%I #7 Sep 08 2012 01:45:29

%S 2,3,7,11,13,17,19,29,41,47,53,61,79,89,107,127,139,149,151,157,167,

%T 179,181,193,197,229,257,283,307,311,317,337,347,349,353,383,389,397,

%U 443,457,463,479,487,491,503,521

%N Primes p such that 42 is a square mod p.

%H Vincenzo Librandi, <a href="/A038921/b038921.txt">Table of n, a(n) for n = 1..1000</a>

%t Select[Prime[Range[100]], ! JacobiSymbol[42, #] == -1 &] (* _Vincenzo Librandi_, Sep 08 2012 *)

%K nonn

%O 1,1

%A _N. J. A. Sloane_.