Generating sequence numbers is one of the most commonly used job in Excel. A sequence number could be numeric (1,2,3,4…) or alphanumeric (AB234,AB235,AB236…) and it could be used as an identifier to a record.
It is difficult when we have to write down the sequence numbers manually in every cell. It is a time consuming task.
So just follow these steps to generate the sequence numbers:
Sequence numbers in a column
In the row , that the sequence numbers have to displayed, enter the numbers in the order. Suppose the sequence number I need are 21,22,23…
 Write 21 in the first cell in the row (A1)
 Write 22 in the next row, but the same column (A2)
 Select both A1 and A2
 Point the mouse to the bottom right corner of the selection
 Drag down to the cells you need and the sequence to be displayed.
Alphanumeric
Sequence numbers in a row
If we need sequence numbers in a row, the same can be done.

Write the sequence in the the first cell(A1)

Write the next sequence in the next column, same row (B1)

Select both A1 and B1

Take the cursor to the bottom right corner of the selection
 Drag sideways till the cell we require the sequence to appear.
The sequence will be interrupted, if we add, move or remove cells and we will have to update the cells as mentioned earlier, which is by choosing 2 cells in the right sequence and dragging it till the last cell.