A033215 Primes of form x^2+21*y^2.

37, 109, 193, 277, 337, 373, 421, 457, 541, 613, 673, 709, 757, 877, 1009, 1033, 1093, 1117, 1129, 1201, 1213, 1297, 1381, 1429, 1453, 1549, 1597, 1621, 1789, 1801, 1873, 1933, 2017, 2053, 2137, 2221

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• easy

References

• David A. Cox, "Primes of the Form x^2 + n y^2", Wiley, 1989.

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)

Crossrefs

Cf. A139643.

Programs

Mathematica

QuadPrimes2[1, 0, 21, 10000] (* see A106856 *)

Formula

Equivalently, primes congruent to {1, 25, or 37} (mod 84). - T. D. Noe, Apr 29 2008 [See e.g. Cox, p. 36. - N. J. A. Sloane, May 27 2014]