Generating functions for the coefficients of the Cremmer-Gervais R-matrices

The coefficients of certain operators on $V\otimes V$ can be constructed using generating functions. Necessary and sufficient conditions are given for some such operators to satisfy the Yang-Baxter equation. As a corollary we obtain a simple, direct proof that the Cremmer-Gervais R-matrices satisfy the Yang-Baxter equation. This approach also clarifies Cremmer and Gervais's original proof via the dynamical Yang-Baxter equation.