EtotalCBS=Fscf_scheme(Etotal,SCFscf_basis)+Fcorl_scheme(Ecorl,corl_wfncorl_basis)+δdelta_wfn_lesserdelta_wfn+δdelta2_wfn_lesserdelta2_wfn+δdelta3_wfn_lesserdelta3_wfn+δdelta4_wfn_lesserdelta4_wfn+δdelta5_wfn_lesserdelta5_wfn

Here, F is an energy or energy extrapolation scheme, and the following also hold.

δdelta_wfn_lesserdelta_wfn=Fdelta_scheme(Ecorl,delta_wfndelta_basis)Fdelta_scheme(Ecorl,delta_wfn_lesserdelta_basis)
δdelta2_wfn_lesserdelta2_wfn=Fdelta2_scheme(Ecorl,delta2_wfndelta2_basis)Fdelta2_scheme(Ecorl,delta2_wfn_lesserdelta2_basis)
δdelta3_wfn_lesserdelta3_wfn=Fdelta3_scheme(Ecorl,delta3_wfndelta3_basis)Fdelta3_scheme(Ecorl,delta3_wfn_lesserdelta3_basis)
δdelta4_wfn_lesserdelta4_wfn=Fdelta4_scheme(Ecorl,delta4_wfndelta4_basis)Fdelta4_scheme(Ecorl,delta4_wfn_lesserdelta4_basis)
δdelta5_wfn_lesserdelta5_wfn=Fdelta5_scheme(Ecorl,delta5_wfndelta5_basis)Fdelta5_scheme(Ecorl,delta5_wfn_lesserdelta5_basis)

A translation of this ungainly equation to example [5] below is as follows. In words, this is a double- and triple-zeta 2-point Helgaker-extrapolated CCSD(T) coupled-cluster correlation correction appended to a triple- and quadruple-zeta 2-point Helgaker-extrapolated MP2 correlation energy appended to a SCF/aug-cc-pVQZ reference energy.

EtotalCBS=Fhighest_1(Etotal,SCFaug-cc-pVQZ)+Fcorl_xtpl_helgaker_2(Ecorl,MP2aug-cc-pV[TQ]Z)+δMP2CCSD(T)
δMP2CCSD(T)=Fcorl_xtpl_helgaker_2(Ecorl,CCSD(T)aug-cc-pV[DT]Z)Fcorl_xtpl_helgaker_2(Ecorl,MP2aug-cc-pV[DT]Z)