  Let $a_{i,j}(n)$ denote the number of walks in $n$ steps from $(0,0)$ to
$(i,j)$, with steps $(\pm 1,0)$ and $(0,\pm 1)$, never touching a point
$(-k,0)$ with $k\ge 0$ after the starting point. \bous and Schaeffer
conjectured a closed form for the number $a_{-i,i}(2n)$ when $i\ge 1$. In this
paper, we prove their conjecture, and give a formula for $a_{-i,i}(2n)$ for
$i\le -1$.
