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https://i.servimg.com/u/f83/14/43/63/45/osc_ta12.jpg[/img][/url]Looks very familiar! Actually, Osc does do exactly the same sort of picture as Alex, even down to the colour change but I can't seem to find any (packed away in a box somewhere). He is a bit more into his times tables these days, I'm slowly learning to love multiples!
Have you seen Cambridge University's Nrich programme? They publish downloadable maths problems for children of all ages and abilities every month. Oscar loves them
http://nrich.maths.org/public/ Since Alex is clearly very number-oriented I highly recommend "Think of a Number" by Johnny Ball. It's a very visual and fun look at numbers including the history of numbers, how numbers are written round the world and some great bits on the discovery of mathematical theorems. Oscar adores that book, he still spends hours poring over it, even after having it for about three years.