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 A106889 Primes of the form 2x^2 + 5y^2. 4
 2, 5, 7, 13, 23, 37, 47, 53, 103, 127, 157, 167, 173, 197, 223, 263, 277, 293, 317, 367, 373, 383, 397, 463, 487, 503, 557, 607, 613, 647, 653, 677, 727, 733, 743, 757, 773, 797, 823, 853, 863, 877, 887, 967, 983, 997, 1013, 1063, 1087, 1093, 1103, 1117 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Discriminant = -40. LINKS Ray Chandler, Table of n, a(n) for n = 1..10000 [First 1000 terms from Vincenzo Librandi] N. J. A. Sloane et al., Binary Quadratic Forms and OEIS (Index to related sequences, programs, references) FORMULA The primes are congruent to {2, 5, 7, 13, 23, 37} (mod 40). - T. D. Noe, May 02 2008 MATHEMATICA QuadPrimes2[2, 0, 5, 10000] (* see A106856 *) PROG (PARI) list(lim)=my(v=List(), w, t); for(x=0, sqrtint(lim\2), w=2*x^2; for(y=0, sqrtint((lim-w)\5), if(isprime(t=w+5*y^2), listput(v, t)))); Set(v) \\ Charles R Greathouse IV, Feb 09 2017 CROSSREFS Cf. A139827. Primes in A020674. Sequence in context: A165319 A094712 A095281 * A155028 A119839 A107057 Adjacent sequences: A106886 A106887 A106888 * A106890 A106891 A106892 KEYWORD nonn,easy AUTHOR T. D. Noe, May 09 2005 STATUS approved

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Last modified December 9 10:28 EST 2022. Contains 358700 sequences. (Running on oeis4.)