... spectrum of Da,b,0(with δ 3).Lemma 3.4. The spectrum of Da,b,0with δ = gcd(a, b) 3 consists of the eigenvalues of Cδ(except 2 and −2) with multiplicity 3, the eigenvalues of Caand ... eigenvalues of Ca∪ Cband be of multiplicity 1.This ends the proof.From the above lemma we know to some extent the spectrum of Da,b,0. If H is atentative cospectral mate of Da,b,0, ... is of multiplicity at least 2 fo r Lg,p. By the Interlacing Theorem a ppliedat the vertex of degree 2 in the path adjacent to the vertex of degree 3, λ must b e aneigenvalue of Cgor of...