adding monkeygrid problem

There is a monkey which can walk around on a planar grid. The monkey can
move one space at a time left, right, up or down. That is, from (x, y)
the monkey can go to (x+1, y), (x-1, y), (x, y+1), and (x, y-1). Points
where the sum of the digits of the absolute value of the x coordinate
plus the sum of the digits of the absolute value of the y coordinate are
lesser than or equal to 19 are accessible to the monkey. For example,
the point (59, 79) is inaccessible because 5 + 9 + 7 + 9 = 30, which is
greater than 19. Another example: the point (-5, -7) is accessible
because abs(-5) + abs(-7) = 5 + 7 = 12, which is less than 19. How many
points can the monkey access if it starts at (0, 0), including (0, 0)
itself?

http://stackoverflow.com/questions/18133918/improve-the-solution-to-monkey-grid-puzzle