Does anyone perhaps know a clever way to select every other group of n entries in a numpy array? For example here Id like to select all "unique" entries 0,1,4,5,8,9 etc. (n=2) without resorting to a sort:

```
[[ 0  2]
 [ 1  3]
 [ 2  0]
 [ 3  1]
 [ 4  6]
 [ 5  7]
 [ 6  4]
 [ 7  5]
 [ 8 10]
 [ 9 11]
 [10  8]
 [11  9]
 [12 14]
 [13 15]
 [14 12]
 [15 13]]

```

Building an index array before hand is an option but I was wondering if anyone had a better idea!