The above shell is a copy of Don's watercolor painting of The Nautilus shell; it is Don's logo. The shell is beautiful, its shape a mathematical curve, and can be obtained from conchking. Also see the equation for the shell , making a spiral , IES java applet making a Nautilus, Xah Lee's work on spirals (and other curves) and student work on the growth of the Nautilus (chapter 6), and Don compares the Spirals of the Nautilus shell, the Fibonacci numbers, and the Equal Tempered Chromatic Music Scale .
Don retired from The Math Program
as of May 30, 2014
On the last day of the school year 2013-2014, Sue, below, received an award for the most improved math student in 5th grade at Holy Cross elementary school. Read what Grandma had to say!