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 A000606 Number of nonnegative solutions to x^2 + y^2 + z^2 <= n. (Formerly M3294 N1329) 7
 1, 4, 7, 8, 11, 17, 20, 20, 23, 29, 35, 38, 39, 45, 51, 51, 54, 63, 69, 72, 78, 84, 87, 87, 90, 99, 111, 115, 115, 127, 133, 133, 136, 142, 151, 157, 163, 169, 178, 178, 184, 199, 205, 208, 211, 223, 229, 229, 230, 239, 254, 260, 266, 278, 290, 290, 296 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 REFERENCES H. Gupta, A Table of Values of N_3(t), Proc. National Institute of Sciences of India, 13 (1947), 35-63. N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence). N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS T. D. Noe, Table of n, a(n) for n = 0..1000 FORMULA G.f.: (1/(1 - x))*(Sum_{k>=0} x^(k^2))^3. - Ilya Gutkovskiy, Mar 14 2017 MATHEMATICA nn = 50; t = Table[0, {nn}]; Do[d = x^2 + y^2 + z^2; If[0 < d <= nn, t[[d]]++], {x, 0, nn}, {y, 0, nn}, {z, 0, nn}]; Accumulate[Join[{1}, t]] (* T. D. Noe, Apr 01 2013 *) PROG (Python) for n in range(99):   k = 0   for x in range(99):     s = x*x     if s>n: break     for y in range(99):         sy = s + y*y         if sy>n: break         for z in range(99):             sz = sy + z*z             if sz>n: break             k+=1   print str(k)+', ', # Alex Ratushnyak, Apr 01 2013 CROSSREFS Cf. A000604, A117609. Cf. A002102 (first differences). Sequence in context: A190765 A024621 A296029 * A215458 A061932 A270336 Adjacent sequences:  A000603 A000604 A000605 * A000607 A000608 A000609 KEYWORD nonn AUTHOR EXTENSIONS More terms from Sean A. Irvine, Dec 01 2010 STATUS approved

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Last modified November 12 19:19 EST 2018. Contains 317116 sequences. (Running on oeis4.)