Adjoining cells in the table of HTML can be spanned into one, with their topological consistency being under questions. For instance, after 9 cells have been arranged into the shape of 3x3 (No. 51), you can rearrange it into 8 cells (No. 52) by spanning only one place. On the other hand, it is no longer 3x3 but 1x1 if you rearrange it into 1 cell by spanning all the places. You can keep the shape of 3x3 as long as it contains either of 7 cells (No. 53), 6 cells (No. 54) or 5 cells (No. 55). As a side note, No. 54 is a part of No. 13, and No. 55 is of No. 12.
(cf.) Source and Execution: List
Hideki Nakazawa 2011
Appeared in the Bulletin "New-Method" No. 9
Japanese | New-Method | Hideki Nakazawa