IMO 1989 LL ICE40
A sequence of real numbers x0, x1, x2, . . . is defined as follows:
IMO 1989 LL ICE40
Origin: ICE
Problem
A sequence of real numbers x0, x1, x2, . . . is defined as follows: x0 = 1989 and for each n \geq1 xn = −1989 n n−1 k=0 xk. Calculate the value of 1989 n=0 2nxn.