# Summation of odd power

How do I find the explicit formula for the following summation: $x^1 + x^3 + x^5 + ...$

I know $1 + x + x^2 + x^3 + ... = 1/(1-x)$, but this is quite a different series.

$$x+x^3+x^5+....=x(1+x^2+x^4+....)=x(1+(x^2)^1+(x^2)^2+(x^2)^3+....)=\frac {x}{1-x^2}$$

• Thanks! why didnt I think of this?! – AbcXYZ Dec 7 '12 at 11:19
• So clever, Amr! :-) – 000 Dec 7 '12 at 11:29
• Thank you. But I am not that clever really for posting this answer – Amr Dec 7 '12 at 11:30

Not much different,$$x^1+x^3+x^5\cdots=x(1+x^2+(x^2)^2+\cdots)$$

• Edited the formula, as it was not correct... – Jan Keersmaekers Dec 7 '12 at 11:06