MathDB
Problem 12 IMC 2004 Macedonia

Source:

July 26, 2004
linear algebramatrixIMCcollege contests

Problem Statement

For n0 n\geq 0 define the matrices An A_n and Bn B_n as follows: A_0 \equal{} B_0 \equal{} (1), and for every n>0 n>0 let A_n \equal{} \left( \begin{array}{cc} A_{n \minus{} 1} & A_{n \minus{} 1} \\ A_{n \minus{} 1} & B_{n \minus{} 1} \\ \end{array} \right) \ \textrm{and} \ B_n \equal{} \left( \begin{array}{cc} A_{n \minus{} 1} & A_{n \minus{} 1} \\ A_{n \minus{} 1} & 0 \\ \end{array} \right). Denote by S(M) S(M) the sum of all the elements of a matrix M M. Prove that S(A_n^{k \minus{} 1}) \equal{} S(A_k^{n \minus{} 1}), for all n,k2 n,k\geq 2.