A211509 - OEIS

A211509

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

0, 1, 0, 2, 3, 4, 4, 4, 8, 7, 6, 10, 10, 8, 16, 10, 11, 16, 14, 8, 22, 12, 18, 24, 18, 13, 26, 18, 20, 24, 24, 10, 36, 22, 20, 30, 29, 20, 42, 20, 22, 30, 36, 24, 44, 24, 28, 40, 38, 15, 48, 26, 34, 48, 38, 18, 50, 38, 42, 38, 44, 18, 66, 42, 35, 50, 38, 32, 68, 24, 36

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,4

COMMENTS

For a guide to related sequences, see A211422.

LINKS

Table of n, a(n) for n=0..70.

MATHEMATICA

t[n_] := t[n] = Flatten[Table[w^2 + x*y - 2 n, {w, 1, n}, {x, 1, n}, {y, 1, n}]]

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

t = Table[c[n], {n, 0, 70}] (* A211509 *)

CROSSREFS