16 16 b - a --------- 2 2 b - a
(b^16 - a^16)/(b^2 - a^2)
16 16 a - b --------- 2 2 a - b
14 14 2 12 4 10 6 8 8 6 10 4 12 2 a + b + a *b + a *b + a *b + a *b + a *b + a *b
/ 2 2\ / 4 4\ / 8 8\ \a + b /*\a + b /*\a + b /