Matrices And Determinants

Let \(A = \left( {\matrix{ 1 & { - 1} & 0 \cr 0 & 1 & { - 1} \cr 0 & 0 & 1 \cr } } \right)\) and B = 7A²⁰ \(-\) 20A⁷ + 2I, where I is an identity matrix of order 3 \(\times\) 3. If B = [b_ij], then b₁₃is equal to _____________.