MathDB

Problem 4, Olympic Revenge 2010

Source: IX Olympic Revenge - 2010

January 28, 2013

algebra proposedalgebra

Problem Statement

Let

a_n

and

b_n

to be two sequences defined as below:

i)

a_1 = 1

ii)

a_n + b_n = 6n - 1

iii)

a_{n+1}

is the least positive integer different of

a_1, a_2, \ldots, a_n, b_1, b_2, \ldots, b_n

.
Determine

a_{2009}

.

Back to Problems View on AoPS