A211426 - OEIS

%I #4 Apr 15 2012 14:18:09

%S 1,5,17,21,33,37,49,53,73,93,105,109,121,125,137,141,161,165,201,205,

%T 217,221,233,237,257,285,297,317,329,333,345,349,393,397,409,413,449,

%U 453,465,469,489,493,505,509,521,541,553,557,577,613,673,677

%N Number of ordered triples (w,x,y) with all terms in {-n,...,0,...,n} and 2*w^2+x*y=0.

%C For a guide to related sequences, see A211422.

%t t[n_] := t[n] = Flatten[Table[2 w^2 + x*y, {w, -n, n}, {x, -n, n}, {y, -n, n}]]

%t c[n_] := Count[t[n], 0]

%t t = Table[c[n], {n, 0, 70}]  (* A211426 *)

%t (t - 1)/4                    (* integers *)

%Y Cf. A211422.

%K nonn

%O 0,2

%A _Clark Kimberling_, Apr 10 2012