keep every other element than the nth 1,2,3,4,5,6,7,8,9.takeEveryNth(3) -> 2,3,5,6,8,9
1,2,3,4,5,6,7,8,9
2,3,5,6,8,9
Iterable<T> takeEveryNotNth(int n) => whereIndexed((i, _) => i % n != 0);