VOOZH about

URL: https://oeis.org/A106861

⇱ A106861 - OEIS

login
A106861
Primes of the form x^2+xy+4y^2, with x and y nonnegative.
2
19, 31, 79, 109, 151, 181, 199, 211, 229, 271, 331, 349, 409, 421, 439, 499, 571, 601, 619, 631, 661, 691, 709, 769, 811, 829, 859, 919, 991, 1021, 1039, 1051, 1069, 1129, 1171, 1201, 1249, 1291, 1321, 1381, 1399, 1429, 1459, 1471, 1489, 1531, 1579
OFFSET
1,1
COMMENTS
Discriminant=-15.
Subset of A033212. - Robert Israel, Jul 25 2014
LINKS
Vincenzo Librandi and Rick L. Shepherd, Table of n, a(n) for n = 1..10000 (first 2000 terms from Vincenzo Librandi)
N. J. A. Sloane et al., Binary Quadratic Forms and OEIS (Index to related sequences, programs, references)
MAPLE
N:= 1000; # to get all terms <= N
Primes:= select(isprime, [seq(2*n+1, n=1..floor((N-1)/2))]):
filter:= proc(p) local S;
S:= remove(hastype, [isolve(x^2+x*y+4*y^2=p)], negint);
nops(S) > 0
end proc:
A:= select(filter, Primes); # Robert Israel, Jul 25 2014
MATHEMATICA
QuadPrimes2[1, 1, 4, 1000000] (* see A106856 *)
CROSSREFS
Cf. A033212.
Sequence in context: A104227 A274507 A032743 * A107168 A243450 A237418
KEYWORD
nonn,easy
AUTHOR
T. D. Noe, May 09 2005
STATUS
approved