N 3 n 1 2 July 8, 2019 16 32 64 128 N 3 5 n 1 2 N 4 n 3 1 2 N 3 2n 1 3n 2 N 3 1 2 12 1 2 3 n n 1 2 induction 3 n 1 2n 3 n 1 27 N 3n 1 )/ 2 N 2 /( n 3 1 convergent or divergent (- 1 n x 3 n 2n 1 N 2 2n 3 n 1 5 n 3 n 2 2n 1 1 2 3 n n n 1 )/ 2 proof 1 2 3 n n n 1 )/ 2 доказать