On the maximum number of open triangles in graphs with the same number of vertices and edges

An open triangle (OT) is a $3$-vertex subgraph with two edges, i. e. an induced path of length $2$. A formula for the maximum number of OT in $n$-vertex graphs with $n$ edges is proved in the paper. We also present a full characterization of graphs for which the maximum is attained. Illustr. 2, bibliogr. 10.