Seasons
Season 1
6 episodes
1971
Season 2
10 episodes
1972
Season 3
10 episodes
1973
Season 4
10 episodes
1974
Season 5
10 episodes
1975
Season 6
10 episodes
1976
Season 7
10 episodes
1977
Season 8
10 episodes
1978
Season 9
10 episodes
1979
Season 10
10 episodes
1980
Season 11
10 episodes
1981
Season 12
10 episodes
1982
Season 13
10 episodes
1983
Season 14
10 episodes
1984
Season 15
10 episodes
1985
Season 16
7 episodes
1986
Season 17
29 episodes
2011
Season 18
10 episodes
2013