When you’re studying algorithms, there is a number of series and expression that keep showing up. A while ago, I discussed the special form . But that’s not the only one. Another form that keeps showing up is
We can look the particular form this sum takes for specific in some compendium (like CRC’s tables and formulae, that have seen 30-something editions over the last half century), or… you can find the formula yourself. It’s a bit tedious, but not that complicated.