By a lucky coincidence the lengths match up. In the 1x case,
the result is a single 48-bit quantity. In the 2x case,
the result is two 24-bit quantities. Finally in the 4x case,
-the rwsult is four 12-bit quantities.
+the result is four 12-bit quantities.
The reason this works is down to the requirement that Partitions be
of equal sizes. 4x 4-bit to be Concatenated with 4x 8-bit, in
the last example.
+Table for 3-way concatenation, divided by partition:
+
+| partition | o3 | o2 | o1 | o0 |
+| 000 | a3 a2 a1 | a0 b3 b2 | b1 b0 c3 | c2 c1 c0 |
+| 111 | a3 b3 c3 | a2 b2 c2 | a1 b1 c1 | a0 b0 c0 |