A106917 Primes of the form 2x^2 + 7y^2.

2, 7, 71, 79, 113, 191, 193, 263, 337, 401, 457, 463, 569, 599, 617, 631, 641, 809, 823, 863, 919, 991, 1009, 1031, 1201, 1289, 1297, 1327, 1367, 1471, 1583, 1607, 1801, 1831, 1913, 1999, 2087, 2111, 2143, 2153, 2297, 2311, 2473, 2521, 2543

Offset

1,1

Comments

Discriminant = -56.

Links

Vincenzo Librandi and 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)

Mathematica

QuadPrimes2[2, 0, 7, 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)\7), if(isprime(t=w+7*y^2), listput(v, t)))); Set(v) \\ Charles R Greathouse IV, Feb 09 2017

Crossrefs

Sequence in context: A260566 A113866 A165978 * A188665 A198188 A230459

Adjacent sequences: A106914 A106915 A106916 * A106918 A106919 A106920

Keyword

nonn,easy

Author

T. D. Noe, May 09 2005

Status

approved