Number Series - General Questions

Look at this series: 6, 20, 62, 188, 566, 1700, … What number should come next?

Look at this series and find the number that does not belong: 3, 9, 27, 80, 243, 729, 2187

Look at this series: 51, 56, 61, 66, 71, 76, … What number should come next?

Look at this series: 130, 121, 112, 103, 94, 85, … What number should come next?

Look at this series and find the number that does not belong: 1, 3, 4, 7, 11, 21, 29