We have thus shown a one-to-one correspondence and we are done.
It should also be noted that if we take a Ferrers diagram of a partition and reflect it about the
45◦ downward slanting line through the upper left dot we would obtain the same partition as when
we count the dots by the columns rather than the rows. Let’s try this with 3 + 3 + 2 + 1 + 1. We
start off with the diagram on the left, reflect it about the 45◦
line, and end up with the diagram
on the right: