The scope of applicability of correlated quantum chemical methods is limited by their steep scaling with respect to the system size . To formulate the algorithms in terms of basic linear algebra operations such as matrix multiplication, many-body wave functions are represented by Slater determinants composed of molecular orbitals, which are, in turn, represented as an expansion over one-electron basis sets (i.e., atomic orbitals). Consequently, the ultimate scaling of a many-body method is determined not only by the number of electrons, but also by the number of basis functions. For example, the overall N 6 scaling of the coupled-cluster method with single and double excitations (CCSD) comes from the computational step involving O 2 V 4 operations, where O and V denote the number of occupied and virtual orbitals, respectively . Whereas the former is determined by the number of electrons, the latter depends on the number of basis functions. Full inclusion of triple excitations, as in CCSDT , leads to N 8 complexity, while perturbative treatments of triples, such as in (T) , ( T) , , (dT) , (fT) , and related approaches , give rise to N 7 scaling.