# Now recursively generate the ternary tree.
        # (Note that the terms are the same in each branch except for sign.)

        # Branch 1 (+-+):
        $i =   $a - 2*$b + 2*$h;
        $j = 2*$a -   $b + 2*$h;
        $k = 2*$a - 2*$b + 3*$h;
        &generate($i,$j,$k);

        # Branch 2 (+++):
        $i =   $a + 2*$b + 2*$h;
        $j = 2*$a +   $b + 2*$h;
        $k = 2*$a + 2*$b + 3*$h;
        &generate($i,$j,$k);

        # Branch 3 (-++):
        $i =   -$a + 2*$b + 2*$h;
        $j = -2*$a +   $b + 2*$h;
        $k = -2*$a + 2*$b + 3*$h;
        &generate($i,$j,$k);