The term popped up on xkcd:
The answer btw is 4/pi - 1/2. You can get it either analytically or numerically.
Then this popped up on SMBC today:
Sometimes work feels like this.
Next question: replace each of the resistors in the xkcd problem with a 1pF capacitor and a 1uH inductor, wired in series. What will be the resulting impedance, as a function of input frequency?