MathDB
Determine maximum and minimum value of a(n) over n <= 1996

Source: IMO Shortlist 1996, A9

August 9, 2008
floor functionmodular arithmeticalgebraSequencerecurrence relationIMO Shortlist

Problem Statement

Let the sequence a(n), n \equal{} 1,2,3, \ldots be generated as follows with a(1) \equal{} 0, and for n>1: n > 1: a(n) \equal{} a\left( \left \lfloor \frac{n}{2} \right \rfloor \right) \plus{} (\minus{}1)^{\frac{n(n\plus{}1)}{2}}. 1.) Determine the maximum and minimum value of a(n) a(n) over n1996 n \leq 1996 and find all n1996 n \leq 1996 for which these extreme values are attained. 2.) How many terms a(n),n1996, a(n), n \leq 1996, are equal to 0?