User blog comment:Wythagoras/Extension to Friedmann's stuff/@comment-1605058-20130612190549/@comment-10429372-20130613051701

In a 2-dimensional field, for example:

1221

2211

1212

1211

are the subsequences:

22  221

12  212  12  211

12  211  12  212

They leap in both dimensions from i to 2i.