Hello, That sequence had a reference but it was a little obscure if I remember well. I think that Neil Sloane has a copy of the original article somewhere. Casket are boxes or boîtes in french. http://www.google.com/search?num=100&hl=en&hs=xyp&lr=&safe=off&client=firefox-a&rls=org.mozilla:en-US:official&pwst=1&oi=defmore&q=define:casket Simon Plouffe