For some reason the 555 output pin has -15Ω resistance. This enables it to power a simple LC negative resistance oscillator that wouldn’t actually work in real life when configured as shown here due to a lack of conservation of energy. Unless it made itself cold in the process (like a normal resistor converts electrical power to heat a negative one converts heat to electricity), but it would then violate a different law of thermodynamics (because it would decrease the entropy of a closed system, assuming it were a closed system).
