Number puzzle

A very quick guess would be 196.

Nope...

Come on, find out the true rule beneath them

How about 155?

3 = 1 * 3
14 = 2 * 7 (7 = 3 + 4)
39 = 3 * 13 (13 = 7 + 6)
84 = 4 * 21 (21 = 13 + 8)
155 = 5 * 31 (31 = 21 + 10)

Wow, that's great!
there's another approach of getting it.

3=1*(1+1)+1^3
14=2*(2+1)+2^3
39=3*(3+1)+3^3
84=4*(4+1)+4^3
155=5*(5+1)+5^3
..........
?=n*(n+1)+n^3