Yeah, I don’t believe it would be possible to come up with this (or the solutions on MathPages that I forgot to link, thank you Shankar) ex nihilo in the context of a job interview, unless one happened to be Ramanujan himself. If I saw something like this in an interview I would assume that they were looking for how the interviewee deals with an intractable problem. That said, it looks like the Google test that this was a part of was a take-home thing, so you could just look up the answer.
Yeah, I don’t believe it would be possible to come up with this (or the solutions on MathPages that I forgot to link, thank you Shankar) ex nihilo in the context of a job interview, unless one happened to be Ramanujan himself. If I saw something like this in an interview I would assume that they were looking for how the interviewee deals with an intractable problem. That said, it looks like the Google test that this was a part of was a take-home thing, so you could just look up the answer.
(I don’t know that I would be able to do this even numerically without having happened to have recently read a paper which mentioned the effective resistance)