Do you want to feed manually ?
In this case, you enter the 2 first figures, select the two cells and drag them down. Excel will increment automatically.
Do you want a formula ?
Do you want to feed form a macro ?
Then it will be a loop such as :
For i=1 to xxx 'if you begin at row 1
activesheet.cells(i,1)=activesheet.cells(i-1,1)+1 'if you work on column 1
Bur a more precise macro can be designed only with more precise info.