4 1 - x ------ 1 - x
(1 - x^4)/(1 - x)
4 -1 + x ------- -1 + x
(-1 + x^4)/(-1 + x)
1 + x + x^2 + x^3
2 3 1 + x + x + x
(1.0 - x^4)/(1.0 - x)
/ 2\ (1 + x)*\1 + x /
(1 + x)*(1 + x^2)