Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.
%I #19 Oct 06 2018 09:29:00
%S 1,2,0,0,8,12,0,0,24,26,0,0,32,28,0,0,24,36,0,0,48,64,0,0,96,62,0,0,
%T 64,60,0,0,24,96,0,0,104,76,0,0,144,84,0,0,96,156,0,0,96,114,0,0,112,
%U 108,0,0,192,160,0,0,192,124,0,0,24,168,0,0,144,192,0
%N Number of integer solutions to a^2 + 4*b^2 + 4*c^2 + 4*d^2 = n.
%H Seiichi Manyama, <a href="/A236925/b236925.txt">Table of n, a(n) for n = 0..10000</a>
%H Olivia X. M. Yao, Ernest X. W. Xia, <a href="https://doi.org/10.1016/j.disc.2013.11.011">Combinatorial proofs of five formulas of Liouville</a>, Discrete Math. 318 (2014), 1--9. MR3141622.
%F Yao and Xia give an explicit formula for a(n) due to Liouville.
%F G.f.: theta_3(q)*theta_3(q^4)^3, where theta_3() is the Jacobi theta function. - _Ilya Gutkovskiy_, Aug 03 2018
%Y Cf. A000118.
%K nonn,look
%O 0,2
%A _N. J. A. Sloane_, Feb 14 2014