[math-fun] Thanks for the replies about sums of squares ...

As is so often the case, once someone points out the answer you feel stupid for not having seen it yourself. My thanks to Tomas Rokicki and Gareth McCaughan for making me feel stupid <grin> Cheers! Colin -- Now available: "Bridges of Dee - Colour and Composition" http://www.williamsonfineart.co.uk/pages/bridges.html