Hi,

Suppose A=(a_{ij}) is a symmetric positive-definite matrix. The sum of the elements of A^m can be found as: S=\sum_{k_1,\ldots,k_{m+1}}a_{k_1k_2}\cdot\ldots\c  dot a_{k_mk_{m+1}}.
I need to know if \[S=\sum_{k_1,\ldots,k_m}a_{k_1k_2}\cdot\ldots\cdot a_{k_{m-1}k_m}a_{k_mk_m}+2\sum_{k_1,\ldots,k_m}a_{k_1k_2}\  cdot\ldots\cdot a_{k_{m-1}k_m}\sum_{k_{m+1}=1}^{k_m-1}a_{k_mk_{m+1}}\].

Thanks in advance.