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Number of inequivalent solutions to x^2+y^2+z^2 = n^2.
12

%I #21 Feb 01 2018 18:56:31

%S 1,1,1,2,1,2,2,2,1,4,2,3,2,3,2,5,1,4,4,4,2,7,3,4,2,5,3,9,2,5,5,5,1,11,

%T 4,7,4,6,4,10,2,7,7,7,3,13,4,7,2,9,5,14,3,8,9,10,2,16,5,9,5,9,5,21,1,

%U 11,11,10,4,17,7,10,4,11,6,18,4,16,10,11,2,23,7,12,7,14,7,20,3

%N Number of inequivalent solutions to x^2+y^2+z^2 = n^2.

%H T. D. Noe, <a href="/A016727/b016727.txt">Table of n, a(n) for n = 0..10000</a>

%H Michael Gilleland, <a href="/selfsimilar.html">Some Self-Similar Integer Sequences</a>

%H C. D. Olds, <a href="http://projecteuclid.org/euclid.bams/1183503695">On the representations N_3(n^2)</a>, Bull. Am. Math. Soc. 47 (6) (1941) 499-503

%F a(n) = A000164(n^2). - _R. J. Mathar_, Feb 12 2017

%t Table[Length[PowersRepresentations[n^2, 3, 2]], {n, 0, 100}]

%Y Cf. A065458.

%Y Column k=3 of A255212.

%K nonn

%O 0,4

%A csvcjld(AT)nomvst.lsumc.edu