A spectral characterization of the $s$-clique extension of the triangular graphs

A regular graph is co-edge regular if there exists a constant $mu$ such that any two distinct and non-adjacent vertices have exactly $mu$ common neighbors. In this paper, we show that for integers $sge 2$ and $n$ large enough, any co-edge-regular graph which is cospectral with the $s$-clique extension of the triangular graph $T((n)$ is exactly the $s$-clique extension of the triangular graph $T(n)$.