θ2⁡(4⁢z|4⁢τ)=B⁢θ2⁡(18⁢π-z|τ)⁢θ2⁡(18⁢π+z|τ)⁢θ2⁡(38⁢π-z|τ)⁢θ2⁡(38⁢π+z|τ),