How do I write $F_1+F_3+F_5+\ldots+F_{2n-1}$ in summation notation? How do I write $F_1+F_3+F_5+\ldots+F_{2n-1}$ in summation notation?
$F_i$ represents the Fibonacci sequence. I can't figure out how to write this in summation notation. Clear steps would be marvelous.

Since the index is odd, ie $\{1,3,5,7,...\}$ then $2n+1$ gives the odd numbers for $n \geq 0$. In summation form it is seen to be
$$\sum_{n=0}^{m-1} F_{2n+1}$$ 
