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A216286 Primes which cannot be written as x^2+5*y^2, where x > 0, y > 0. 1

%I #15 Jan 25 2014 16:39:17

%S 2,3,5,7,11,13,17,19,23,31,37,43,47,53,59,67,71,73,79,83,97,103,107,

%T 113,127,131,137,139,151,157,163,167,173,179,191,193,197,199,211,223,

%U 227,233,239,251,257,263,271,277,283,293,307,311,313,317,331,337,347,353,359,367,373,379,383,397,419

%N Primes which cannot be written as x^2+5*y^2, where x > 0, y > 0.

%C This consists of 5 together with those primes which are not congruent to 1 or 9 (mod 20) (which are listed in A216277). - _N. J. A. Sloane_, Sep 04 2012

%D David A. Cox, Primes of the Form x^2 + n y^2, Wiley, 1989. See Eq. (1.20), p. 19 and Eq. (2.22), p. 32. - _N. J. A. Sloane_, Sep 03 2012

%Y Cf. A033205, A216277.

%K nonn

%O 1,1

%A _V. Raman_, Sep 03 2012

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Last modified April 16 03:22 EDT 2024. Contains 371696 sequences. (Running on oeis4.)