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A125203
Number of ways to write n as 4*x*y - x - y with 1<=x<=y.
6
0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 0, 2, 0, 0, 1, 1, 0, 1, 1, 0, 1, 0, 0, 1, 0, 1, 2, 0, 0, 1, 0, 0, 2, 0, 0, 1, 0, 1, 1, 1, 0, 2, 0, 0, 1, 0, 1, 1, 1, 0, 1, 0, 0, 2, 0, 0, 2, 0, 0, 2, 1, 0, 1, 0, 0, 1, 0, 1, 1, 0, 1, 2, 0, 0, 2, 1, 0, 1, 0, 0, 1, 2, 0, 1, 0, 0, 2, 0, 1, 1, 0
OFFSET
1,26
COMMENTS
a(A094178(n))=0; a(A124934(n))>0; a(A125217(n))=1; a(A125218(n))>1.
LINKS
MATHEMATICA
a[n_] := Solve[1<=x<=y && n == 4 x y - x - y, {x, y}, Integers] // Length;
Table[a[n], {n, 1, 105}] (* Jean-François Alcover, Oct 12 2021 *)
PROG
(Haskell)
a125203 n = length [() | x <- [1 .. (n + 1) `div` 3],
let (y, m) = divMod (x + n) (4 * x - 1),
x <= y, m == 0]
-- Reinhard Zumkeller, Jan 02 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Nov 24 2006
STATUS
approved