Hi,

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

Thanks in advance.