Large N Elliptic Genus and AdS/CFT Correspondence

According to one of Maldacena's dualities, type IIB string theory on AdS_3 X S^3 X K3 is equivalent to a certain N=(4,4) superconformal field theory. In this note we compute the elliptic genus of the boundary theory in the supergravity approximation. A finite quantity is obtained once we introduce a particular exclusion principle. In the regime where the supergravity approximation is reliable, we find exact agreement with the elliptic genus of a sigma model with target space K3^N/S_N.