Wigner 6j symbols for SU(N): Symbols with at least two quark-lines

We study a class of SU(N) Wigner 6j symbols involving two fundamental representations, and derive explicit formulae for all 6j symbols in this class. Our formulae express the 6j symbols in terms of the dimensions of the involved representations, and they are thereby functions of N. We view these explicit formulae as a first step towards efficiently decomposing SU(N) color structures in terms of group invariants.