Precedence, d'oh! rs *= (n-(i-1))/i is equivalent to: rs = rs * ((n-(i-1))/i)
not rs = rs * (n-(i-1))/i which is the same as rs = ( rs * (n-(i-1)) ) /i Ken Iverson was right. Precedence is a bad idea. -- https://mail.python.org/mailman/listinfo/python-list