A211426 - OEIS

A211426

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

1, 5, 17, 21, 33, 37, 49, 53, 73, 93, 105, 109, 121, 125, 137, 141, 161, 165, 201, 205, 217, 221, 233, 237, 257, 285, 297, 317, 329, 333, 345, 349, 393, 397, 409, 413, 449, 453, 465, 469, 489, 493, 505, 509, 521, 541, 553, 557, 577, 613, 673, 677

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OFFSET

0,2

COMMENTS

For a guide to related sequences, see A211422.

LINKS

Table of n, a(n) for n=0..51.

MATHEMATICA

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

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

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

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

CROSSREFS

Cf. A211422.

Sequence in context: A246329 A351176 A211423 * A224513 A302423 A305478

Adjacent sequences: A211423 A211424 A211425 * A211427 A211428 A211429

KEYWORD

nonn

AUTHOR

Clark Kimberling, Apr 10 2012

STATUS

approved