Weierstraß semigroups and nodal curves of type p,q

We study plane curves of type p,q having only nodes as singularities. Every Weierstraß semigroup is the Weierstraß semigroup of such a curve at its place at infinity for properly chosen p,q. We construct plane curves of type p,q with explicitly given nodes and determine their Weierstraß semigroups. Many such semigroups are found.