Let O c be the category of finite-length central-charge-c modules for the Virasoro Lie algebra whose composition factors are irreducible quotients of reducible Verma modules. Recently, it has been shown that O c admits vertex algebraic tensor category structure for any c ∈ C. Here, we determine the structure of this tensor category when c = 13 − 6p − 6p −1 for an integer p > 1. For such c, we prove that O c is rigid, and we construct projective covers of irreducible modules in a natural tensor subcategory O 0 c . We then compute all tensor products involving irreducible modules and their projective covers. Using these tensor product formulas, we show that O c has a semisimplification which, as an abelian category, is the Deligne product of two tensor subcategories that are tensor equivalent to the Kazhdan-Lusztig categories for affine sl 2 at levels −2 + p ±1 . Finally, as a straightforward consequence of the braided tensor category structure on O c together with the theory of vertex operator algebra extensions, we rederive known results for triplet vertex operator algebras W(p), including rigidity, fusion rules, and construction of projective covers. c 5.2. The remaining projective covers 6. Tensor product formulas and semisimplification 6.1. General fusion rules 6.2. Semisimplification 7. On the representation theory of triplet vertex operator algebras References