No I mean that this expression will be incorrect well before the `Long` values themselves overflow:

```
scala> val nPos = 4000000000L
nPos: Long = 4000000000
scala> nPos * (nPos + 1) / 2
res1: Long = -1223372034854775808
```
(Should have said that the problem occurs a little past 3B, not 2B). Sure the 64-bit integer overflows eventually but not worried about quintillions of elements just yet! but having a few billion elements is quite possible.