A106970 Primes of the form x^2-xy+21y^2, with x and y nonnegative.

23, 41, 83, 131, 193, 199, 227, 229, 277, 293, 397, 401, 521, 557, 607, 659, 701, 739, 751, 773, 787, 811, 983, 1013, 1019, 1061, 1117, 1231, 1289, 1409, 1423, 1427, 1447, 1511, 1523, 1531, 1553, 1667, 1669, 1693, 1709, 1723, 1747, 1753, 1847

Offset: 1

Author

T. D. Noe, May 09 2005

Keywords

• nonn
• easy

Comments

Discriminant=-83.

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

Mathematica

QuadPrimes2[1, -1, 21, 10000] (* see A106856 *)