John Sinclair, a poet, music producer and counterculture figure whose lengthy prison sentence after a series of small-time pot busts inspired a John Lennon song and a star-studded 1971 concert to free him, died Tuesday. He was 82. Sinclair drew a nine-and-a-half-to-10-year prison sentence in 1969 for giving two joints to undercover officers in Detroit. He served 29 months, but was released a few days after Lennon, Stevie Wonder, Bob Seger and others performed in front of 15,000 attendees at the University of Michigan’s Crisler Arena. Lennon and his wife, Yoko Ono, performed “John Sinclair,” a song the ex-Beatle wrote that immortalized its subject.