A211647 - OEIS

A211647

Number of ordered triples (w,x,y) with all terms in {1,...,n} and w^2+x^2+y^2<=3n.

0, 1, 4, 7, 11, 17, 23, 32, 38, 48, 60, 66, 78, 87, 102, 114, 121, 139, 157, 169, 178, 196, 214, 232, 241, 263, 284, 296, 314, 329, 359, 371, 386, 410, 434, 452, 471, 495, 516, 540, 555, 582, 612, 630, 651, 678, 702, 729, 738, 772, 805, 829, 853, 871

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OFFSET

0,3

COMMENTS

For a guide to related sequences, see A211422.

LINKS

Table of n, a(n) for n=0..53.

MATHEMATICA

t = Compile[{{n, _Integer}}, Module[{s = 0},

(Do[If[w^2 + x^2 + y^2 <= 3 n, s = s + 1],

{w, 1, #}, {x, 1, #}, {y, 1, #}] &[n]; s)]];

Map[t[#] &, Range[0, 80]] (* A211647 *)