The source of the derivation of the continued fraction part is https://mobile.twitter.com/duetosymmetry/status/1302021471749971970 https://mobile.twitter.com/du

The source of the derivation of the continued fraction part is https://mobile.twitter.com/duetosymmetry/status/1302021471749971970 https://mobile.twitter.com/duetosymmetry/status/130202147174... and it was an attempt to simplify a derivation due to Jacobi. Perhaps he explains how he comes up with it, though you’ll need to be able to read Latin. Possibly this is a relatively standard technique for solving differential equations with continued fractions which people no longer use.