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Consider the function $$\begin{cases} \displaystyle\sum_{r=0}^{2\mu}f(r)(-1)^r\qquad \text{for even $\mu$}\\ \displaystyle\sum_{r=0}^{2\mu}f(r)(-1)^{r+1}\qquad \text{for odd $\mu$}\\\end{cases}$$

Is there a neat notation where the two expressions can be combined into one which will automatically cater for both even and odd values of $\mu$ without splitting into two cases?

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    $\begingroup$ $$(-1)^\mu\sum _{r=0}^{2\mu} f(r)(-1)^r$$ $\endgroup$ Nov 25, 2016 at 16:34
  • $\begingroup$ @ThomasAndrews - Thanks. That works perfectly. Would you like to post this as an answer? I was thinking of using the indicator function but that's probably too cumbersome. $\endgroup$ Nov 25, 2016 at 16:36

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$$\sum_{r=0}^{2\mu}f(r)(-1)^{r+\mu}$$

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  • $\begingroup$ Thanks. That works very well. As mentioned in the comment above, I was thinking of using the indicator function but that's probably too cumbersome. $\endgroup$ Nov 25, 2016 at 16:38

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