A211482 Number of ordered triples (w,x,y) with all terms in {-n,...,0,...,n} and w*x+w*y+x*y=w*x*y.

1, 10, 22, 35, 50, 62, 80, 92, 104, 116, 128, 140, 152, 164, 176, 188, 200, 212, 224, 236, 248, 260, 272, 284, 296, 308, 320, 332, 344, 356, 368, 380, 392, 404, 416, 428, 440, 452, 464, 476, 488, 500, 512, 524, 536, 548, 560, 572, 584, 596, 608, 620

Offset

0,2

Comments

For a guide to related sequences, see A211422.

Links

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

Formula

Conjectures from Colin Barker, May 15 2017: (Start)

G.f.: (1 + 8*x + 3*x^2 + x^3 + 2*x^4 - 3*x^5 + 6*x^6 - 6*x^7) / (1 - x)^2.

a(n) = 12*n + 8 for n>5.

a(n) = 2*a(n-1) - a(n-2) for n>7.

(End)

Mathematica

t[n_] := t[n] = Flatten[Table[w*x + w*y + x*y - w*x*y, {w, -n, n}, {x, -n, n}, {y, -n, n}]]
c[n_] := Count[t[n], 0]
t = Table[c[n], {n, 0, 80}]  (* A211482 *)

Crossrefs

Cf. A211422.

Sequence in context: A232540 A217573 A276626 * A177791 A028569 A014367

Adjacent sequences: A211479 A211480 A211481 * A211483 A211484 A211485

Keyword

nonn

Author

Clark Kimberling, Apr 12 2012

Status

approved