Find the missing number in the sequence.
996, 1000, 992, 1004, 988, ?, 984
1006
1004
1009
1010
1008
1, 2, 3, 5, 8, __, 21
2, 8, 18, 32, 50, 72, (?)
4, 10, 40, 190, 940, ?, 23440
20, 19, 17, __ , 10, 5
56, 42, ?, 20, 12, 6, 2