Extremal spectral result of outerplanar graphs without $P_{3\cdot l}$

Fulong Ye, Yuxiang Liu, Ligong Wang

A graph $G$ is $F$-free if it does not contain $F$ as a subgraph. Let $\mathrm{spex}(n,F)$ be the maximum spectral radius over all $n$-vertex $F$-free outerplanar graphs. For integ…