5) 7, 16, 19, 5, 21, 16, 9, —

This sequence appears to be two interleaved sequences. The first sequence is 7, 19, 21, 9, ... and the second sequence is 16, 5, 16, ... The pattern for the first sequence is +12, +2, -10. The pattern for the second sequence is -11, +11. Assuming the pattern for the first sequence continues with +12, the next number would be 9 + 12 = 21.