Start with 1: O The next square is 4, so add 3: AA AO Next is 9, so add 5: AAA AOO AOO Notice that each time, you are adding 2 * Length of side, plus 1. This was discussed here a while back, relating to Ada Lovelace=20 programming the Babbage machine. Kerry Electron wrote: > Hello, > > analogously to [division] computing the quotient by counting how many tim= es you > can subtract the divisor, you can compute the square root of a number cou= nting > how many times you can subtract sequential odd numbers (1,3,5,7,9,=85). > > [ try it -- it works!]. e.g. 25 -1-3-5-7-9 =3D 0 > > OK, but can someone explain me *why* it works? :-) > > Thanks, > Mario > > =20 --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .