4 x 4 ) 18 3 x 3 July 8, 2019 16 32 64 128 4 x 4 )+ 18 3 x 3 3x 18 4 (- 3 3 4x 31 3 4 x 4 18 5 6 x 6 12 4 x 3 18 9 x 3 4 x 3 4 x 4 x 4 x 4 x 18 + 3