Find the missing term in the series. -1, 2, 7, ?, 23, 34

The missing term is 14.

The differences between consecutive terms grow by 2 each time.

-1 to 2 is +3, 2 to 7 is +5, so the next gap is +7.

Thus the fourth term = 7 + 7 = 14.

Check onward : 14 + 9 = 23 and 23 + 11 = 34.