A169784 - OEIS

%I #15 Jul 11 2020 07:36:27

%S 1,4,4,0,4,10,8,8,4,12,24,0,0,16,8,16,4,8,20,0,10,16,24,8,8,44,8,0,8,

%T 16,40,16,4,16,24,0,12,32,8,16,24,16,16,0,0,50,40,8,0,28,44,0,16,16,

%U 32,40,8,32,40,0,16,32,16,24,4,48,16,0,8,16,80,16,20,40,24,0,0,16,32,32,10,36

%N Number of solutions to a^2 + b^2 + 5*c^2 = n.

%C a(n) = 0 for n of the form 4^i*(8*j+3), A055046. [_Zak Seidov_, May 12 2010]

%H Zak Seidov, <a href="/A169784/b169784.txt">Table of n,a(n) for n=0..1000</a>

%F G.f.: theta_3(q)^2*theta_3(q^5), where theta_3() is the Jacobi theta function. - _Ilya Gutkovskiy_, Aug 01 2018

%Y x^2+y^2+k*z^2: A005875, A014455, A034933, A169783.

%K nonn

%O 0,2

%A _N. J. A. Sloane_, May 12 2010