source 1986 Chudnovsky--Chudnovsky "Sequences of numbers generated by addition in formal groups and new primality and factorization tests", formula 4.9ii, plus common-subexpression elimination compute C1Z1 = C1 Z1 compute C1D1 = C1 D1 compute D1Z1 = D1 Z1 compute D1S1 = D1 S1 compute U = C1Z1^2 compute V = C1D1^2 compute W = D1Z1^2 compute UV = U-V compute S3 = 2 C1Z1 D1S1 compute C3 = U-W+V compute D3 = W-UV compute Z3 = W+UV compute SC3 = S3 C3 compute DZ3 = D3 Z3