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%I #4 Jan 17 2018 09:42:20
%S 1,1,0,3,1,5,141,742,6120,43888,300232,3074478,28901797,290411147,
%T 3175037698,34951274416,399750066121,4814421349467,59532792202344,
%U 768079420764884,10247011240209066,140144002390928732,1978092111496441512,28633995987157024399
%N Number of ordered ways of writing n^2 as a sum of n squares of positive integers.
%H <a href="/index/Su#ssq">Index entries for sequences related to sums of squares</a>
%F a(n) = [x^(n^2)] (Sum_{k>=1} x^(k^2))^n.
%e a(3) = 3 because we have [4, 4, 1], [4, 1, 4] and [1, 4, 4].
%t Table[SeriesCoefficient[(-1 + EllipticTheta[3, 0, x])^n/2^n, {x, 0, n^2}], {n, 0, 23}]
%Y Cf. A037444, A066535, A232173, A287617, A298329.
%K nonn
%O 0,4
%A _Ilya Gutkovskiy_, Jan 17 2018
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