There is a simple applet showing the essence of the inductive proof of this result. To run this applet, you first enter the number *n* you wish to have illustrated; space limitations require *0<n<11*. Then push the [Next] button to step through the stages of the proof.

The base case shown by the applet is *n=1*, although on the proof pages the base case is *n=0*; this is just because there is nothing to show when *n=0*.

Assuming the result for *n* means we know how to sum half of an *n*x*(n+1)* rectangle having rows with *1, 2, ..., n* red dots, respectively. Now we add a new row with all black dots, and then one more red dot to each row. The result is another figure of the same form, but with the parameter *n+1* instead of *n*.

To the first tatami (i.e., proof) page.

To the duck source file.

To the Kumo demos homepage.

To the Tatami Project homepage.

To the UCSD Meaning and Computation Group homepage.