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Numbers of the form 2*x^2 + 5*y^2.
3

%I #26 Jun 07 2019 04:26:14

%S 0,2,5,7,8,13,18,20,22,23,28,32,37,38,45,47,50,52,53,55,63,70,72,77,

%T 80,82,88,92,95,98,103,112,117,118,125,127,128,130,133,143,148,152,

%U 157,162,167,173,175,178,180,182,188,197,198,200,205,207,208,212,220,223,230,242

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

%H Vincenzo Librandi, <a href="/A020674/b020674.txt">Table of n, a(n) for n = 1..7000</a> (corrected by _Sean A. Irvine_, Jun 07, 2019)

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

%Y Cf. A000286, A106889 (primes).

%K easy,nonn

%O 1,2

%A _David W. Wilson_