  We provide formulas for computing the cocycles on a 3-point Witt algebra
Der(R), using an isomorphism between two 3-point algebras Der(R) and Der(S),
where the cocycle is already defined. These cocycles can be used to construct
universal central extensions and the 3-point Virasoro, which are useful for the
representation theory of a 3-point current algebra. The computations
determining the cocycles on Der(R) involve elegant applications of the
Chu-Vandermonde convolution and other identities for sums of binomial
coefficients.
