A020674 Numbers of the form 2*x^2 + 5*y^2.

0, 2, 5, 7, 8, 13, 18, 20, 22, 23, 28, 32, 37, 38, 45, 47, 50, 52, 53, 55, 63, 70, 72, 77, 80, 82, 88, 92, 95, 98, 103, 112, 117, 118, 125, 127, 128, 130, 133, 143, 148, 152, 157, 162, 167, 173, 175, 178, 180, 182, 188, 197, 198, 200, 205, 207, 208, 212, 220, 223, 230, 242

Offset

1,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..7000 (corrected by Sean A. Irvine, Jun 07, 2019)

N. J. A. Sloane et al., Binary Quadratic Forms and OEIS (Index to related sequences, programs, references)

Mathematica

Union[2*First[#]+5*Last[#]&/@(Tuples[Range[0, 10], 2]^2)] (* Harvey P. Dale, May 09 2012 *)

Crossrefs

Cf. A000286, A106889 (primes).

Sequence in context: A280848 A190900 A216572 * A243171 A005624 A275410

Adjacent sequences: A020671 A020672 A020673 * A020675 A020676 A020677

Keyword

easy,nonn

Author

David W. Wilson

Status

approved