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A139501 Primes of the form x^2 + 21x*y + y^2 for x and y nonnegative. 1

%I

%S 23,47,73,101,131,139,163,197,233,239,271,277,311,347,349,353,397,443,

%T 461,463,491,499,541,577,587,593,647,653,691,719,739,761,809,821,823,

%U 853,859,883,929,947,967,997,1013,1051,1061,1087,1151,1163,1223,1277

%N Primes of the form x^2 + 21x*y + y^2 for x and y nonnegative.

%H N. J. A. Sloane et al., <a href="https://oeis.org/wiki/Binary_Quadratic_Forms_and_OEIS">Binary Quadratic Forms and OEIS</a> (Index to related sequences, programs, references)

%t a = {}; w = 21; k = 1; Do[Do[If[PrimeQ[n^2 + w*n*m + k*m^2], AppendTo[a, n^2 + w*n*m + k*m^2]], {n, m, 400}], {m, 1, 400}]; Union[a] (*Artur Jasinski*)

%Y Cf. A139489, A007645, A068228, A007519, A033212, A033212, A107152, A107008, A033215, A107145, A139490, A139491.

%K nonn

%O 1,1

%A _Artur Jasinski_, Apr 24 2008

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Last modified October 22 22:34 EDT 2019. Contains 328335 sequences. (Running on oeis4.)