[math-fun] another (illustrated) commercial

for matrix products <http://gosper.org/foumat.png>. It's a ridiculous png because Mac Mathematica 8+ simply evaporates when I try to save as pdf. If anyone wants the pdf, I believe Neil's Windows 7 Mma 8 will do the job. If anyone wants the 44.7M nb, I'll put it on gosper.org. --rwg