Labelled graphs#11289
Let the number of vertices in a graph be . Compute the number of labelled graphs with vertices (labelled means that the vertices are marked with the numbers from to ). The edges of the graphs are considered undirected, and loops and multiple edges are forbidden.
The number of vertices n~(1 \le n \le 10^5) in the graph.
Print the number of labelled graphs with vertices. Print the answer modulo 10^9 + 7.
Example 1
Example 2