6 3 n 1 2 9 July 8, 2019 16 32 64 128 3 6 9 3n 3n n 1 )/ 2 3 6 9 12 3n 3n n 1 )/ 2 1 3 9 27 pattern rule 6 3•1 2/9 6 (3)+9 (3)