Muharem Kurbegovic, known as The Alphabet Bomber, was a Yugoslav terrorist who fire bombed the Pan AmTerminal at Los Angeles International airport, killing three and injuring eight. He was allegedly motivated to commit the attack after being caught masturbating in a dance hall. His personal vendetta against a judge and the commissioners grew into demands for an end to immigration and naturalization laws, as well as any laws about sex.
In this 2 page letter he challenges his penpal to solve and understand his inserted mathematical pages. You first have to prove you have the brains.