Fast 8 bit unsigned multiplication with 16 bit result. It uses formula
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x*y = ((x+y)/2)^<sup>2 </sup> - ((x-y)/2)^<sup>2</sup>, if x+y is even = ((x+y-1)/2)^<sup>2 </sup> - ((x-y-1)/2)^<sup>2 </sup> + y, if x+y is odd and x>=y
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