Consider the set $$\mathcal{T}$$ of all triangles whose sides are distinct prime numbers which are also in arithmetic progression. Let $$\triangle\in\mathcal{T}$$ be the triangle with the least perimeter. If $$a^\circ$$ is the largest angle of $$\triangle$$ and if $$L$$ is its perimeter, determine the value of $$\frac{a}{L}$$.