acomb_w = [...
1 1
2 1
3 1
4 1
1 2
2 2
3 2
4 2
1 3
2 3
3 3
4 3
1 4
2 4
3 4
4 4];
acomb_w(~diff(acomb_w,1,2),:) = []
... some rows truncated here
