Editing Borwein's algorithm (section)

===Class number 2 (1989)===

Start by setting<ref name="Bailey Borwein 2023">{{cite journal | last=Bailey | first=David H | title=Peter Borwein: A Visionary Mathematician | journal=Notices of the American Mathematical Society | volume=70 | issue=4 | date=2023-04-01 | issn=0002-9920 | doi=10.1090/noti2675 | pages=610–613}}</ref>

:<math> \begin{align} A & = 212175710912 \sqrt{61} + 1657145277365 \\
                      B & = 13773980892672 \sqrt{61} + 107578229802750 \\
                      C & = \left(5280\left(236674+30303\sqrt{61}\right)\right)^3
        \end{align}
</math>

Then

:<math>\frac{1}{\pi} = 12\sum_{n=0}^\infty \frac{ (-1)^n (6n)!\, (A+nB) }{(n!)^3(3n)!\, C^{n+\frac12}}</math>

Each additional term of the partial sum yields approximately 25 digits.