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 A106863 Primes of the form x^2+xy+5y^2. 7
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS 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 LINKS Vincenzo Librandi and Ray Chandler, Table of n, a(n) for n = 1..10000 [First 5000 terms from Vincenzo Librandi] N. J. A. Sloane et al., Binary Quadratic Forms and OEIS (Index to related sequences, programs, references) MATHEMATICA QuadPrimes2[1, -1, 5, 10000] (* see A106856 *) PROG (PARI) select(p->issquare(Mod(p, 19))&&isprime(p), [1..1000]) \\ M. F. Hasler, Jan 15 2016 CROSSREFS Primes in A035243. Sequence in context: A155772 A258992 A020582 * A200569 A110016 A254672 Adjacent sequences:  A106860 A106861 A106862 * A106864 A106865 A106866 KEYWORD nonn,easy AUTHOR T. D. Noe, May 09 2005 STATUS approved

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Last modified April 22 09:59 EDT 2021. Contains 343174 sequences. (Running on oeis4.)