7th Canadian Mathematical Olympiad Problems 1975

7th Canadian Mathematical Olympiad Problems 19751.  Evaluate (1·2·4 + 2·4·8 + 3·6·12 + 4·8·16 + ... + n·2n·4n)1/3/(1·3·9 + 2·6·18 + 3·9·27 + 4·12·36 + ... + n·3n·9n)1/3. 2.  Define the real sequence a1, a2, a3, ... by a1 = 1/2, n2an = a1 + a2 + ... + an. Evaluate an.