Group inverses of $\{0,1\}$-triangular matrices and Fibonacci numbers

Manami Chatterjee, K. C. Sivakumar

A number $s$ is the sum of the entries of the inverse of an $n\times n,(n\ge 3)$ upper triangular matrix with entries from the set $\{0,1\}$ if and only if $s$ is an integer l…