A211511 - OEIS

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A211511

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

0, 0, 2, 2, 4, 4, 6, 6, 10, 12, 14, 14, 18, 18, 20, 20, 24, 24, 30, 30, 32, 32, 34, 34, 40, 44, 46, 48, 50, 50, 54, 54, 62, 62, 64, 64, 72, 72, 74, 74, 80, 80, 82, 82, 84, 86, 88, 88, 94, 100, 110, 110, 112, 112, 118, 118, 124, 124, 126, 126, 132, 132, 134, 136

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

OFFSET

0,3

COMMENTS

For a guide to related sequences, see A211422.

LINKS

Table of n, a(n) for n=0..63.

MATHEMATICA

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

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

t = Table[c[n], {n, 0, 60}] (* A211511 *)

t/2 (* integers *)