Abstract:
Let $\Gamma$ be a connected edge-regular graph with parameters $(v,k,\lambda)$, and let $b_1=k-\lambda-1$. It is well-known that, if $b_1=1$, then $\Gamma$ is either a polygon or a complete multipartite graph with parts of order 2. Graphs with $b_1\le4$ were classified earlier. The investigation of graphs even in the case $b_1=5$ involves great difficulties. However, for strongly regular graphs, the situation is much simpler. In this paper, we classify strongly regular graphs with $b_1<24$.