  We study the 4d/2d AGT correspondence between four-dimensional instanton
counting and two-dimensional conformal blocks for generalized SU(2) quiver
gauge theories coming from punctured Gaiotto curves of arbitrary genus. We
propose a conformal block description that corresponds to the elementary SU(2)
trifundamental half-hypermultiplet, and check it against Sp(1)-SO(4) instanton
counting.
