A139660 Primes of the form x^2 + 385*y^2.

389, 401, 421, 449, 641, 709, 1061, 1409, 1549, 1621, 1709, 1901, 2069, 2269, 2381, 2689, 2909, 3061, 3089, 3221, 3301, 3389, 3469, 3529, 4229, 4349, 4481, 4621, 4789, 4909, 5009, 5021, 5261, 5569, 5581, 5861, 6029, 6301, 6329, 6449, 6469

Offset: 1

Author

T. D. Noe, Apr 29 2008

Keywords

• nonn
• easy

Comments

Discriminant=-1540. See A139643 for more information.

The primes are congruent to {1, 9, 81, 141, 169, 221, 289, 309, 361, 389, 401, 421, 449, 529, 641, 669, 709, 729, 841, 949, 961, 1061, 1101, 1149, 1241, 1269, 1369, 1401, 1409, 1521} (mod 1540).

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)

Programs

Magma

k:=385; [p: p in PrimesUpTo(6500) | NormEquation(k, p) eq true]; // Bruno Berselli, Jun 01 2016

Mathematica

QuadPrimes2[1, 0, 385, 10000] (* see A106856 *)