a1+b0⁢b1b1-a1⁢a2⁢b3/b1a2⁢b3+b1⁢(a3+b2⁢b3)-a3⁢a4⁢b1⁢b5a4⁢b5+b3⁢(a5+b4⁢b5)-a5⁢a6⁢b3⁢b7a6⁢b7+b5⁢(a7+b6⁢b7)-⋯.