Harry Nilsson was inspired to write this song after getting a busy signal on a phone call. For those of you too young to remember busy signals, yes, it’s absolutely enough to throw you into an existential funk. A busy signal is the sound of rejection and unwantedness. There’s nothing like a late night busy signal from a loved one to make you dwell on how essentially solitary and inconsequential your existence is. You may even, like Harry, begin to imagine the mathematical equations of your loneliness, and arrive at the conclusion that all sums are divided by one, and you will always be the 1 divided against all the others. Math makes everything more depressing.