1. Type in a sequence of numbers.
Note: For the AutoFill to continue the sequence in order, you have to type in at least two consecutive numbers, e.g. 1, 2. If you only type in 1, the AutoFill will fill in all the cells with the same number.
vs.
2. Select the cells and drag them down by the little dot in the corner.
3. MobiSheets will autocomplete the sequence.