"3 Is a Magic Number"...
In 1971, Bob Dorough received a commission to "set the multiplication tables to music." And this was the beginning of Schoolhouse Rock on ABC tv, a Saturday morning cartoon series that entertained and enlightened children from 1973-1985.
Read lots more about Bob at http://www.bobdorough.com/bio.htm.
Blind Melon covered the song in 1995: