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Number of points in N^4 of norm <= n.
5

%I #11 Sep 29 2019 13:19:56

%S 1,5,20,70,165,357,688,1154,1867,2907,4272,6070,8357,11307,14998,

%T 19470,24809,31211,38928,47816,58201,70361,83962,99648,117519,137521,

%U 160270,185528,213615,244649,279370,317006,358809,404823,454838,509486,568493

%N Number of points in N^4 of norm <= n.

%H Andrew Howroyd, <a href="/A055403/b055403.txt">Table of n, a(n) for n = 0..500</a>

%F a(n) = [x^(n^2)] (1 + theta_3(x))^4/(16*(1 - x)), where theta_3() is the Jacobi theta function. - _Ilya Gutkovskiy_, Apr 15 2018

%Y Column k=4 of A302998.

%K nonn

%O 0,2

%A _David W. Wilson_