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A106863
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Primes of the form x^2+xy+5y^2.
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8
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5, 7, 11, 17, 19, 23, 43, 47, 61, 73, 83, 101, 131, 137, 139, 149, 157, 163, 191, 197, 199, 229, 233, 239, 251, 263, 271, 277, 283, 311, 313, 347, 349, 353, 359, 367, 389, 397, 419, 443, 457, 461, 463, 467, 479, 491, 499, 503, 541, 557, 571, 577, 587, 593
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OFFSET
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1,1
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COMMENTS
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Discriminant=-19.
Also, primes of the form x^2-xy+5y^2 with x and y nonnegative.
Also, primes which are a square (mod 19) (or, (mod 38) - cf. A191028). - M. F. Hasler, Jan 15 2016
Also, primes p such that Legendre(-2,p) = 0 or 1. - N. J. A. Sloane, Dec 25 2017
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LINKS
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MATHEMATICA
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QuadPrimes2[1, -1, 5, 10000] (* see A106856 *)
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PROG
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(PARI) select(p->issquare(Mod(p, 19))&&isprime(p), [1..1000]) \\ M. F. Hasler, Jan 15 2016
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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