A quick Google search found “Logic Friday”, available at sontrak.com. Boolean operations can be described using logic gates, truth tables or an equation.
There is lots to find: weather information, humorous IRC style chat, worldwide operators trying to reach as far as possible and even digitally coded pictures.
Rich suggested using a square wave oscillator with a filter to turn it into a sine wave. The filter attenuates all frequencies except the fundamental frequency, which should remove much of the square wave. Over a couple of nights I tested this in ltspice then built it on a breadboard and checked the real life results.