Alternately, type 10000 in first cell, 20000 in second cell.
Highlight both cells, go to right bottom corner of the selected range (you will see solid black cross). Drag selection down (or across depending on how first 2 cell is arranged).
Hi
Say example in cell A1 Type 1
& in cell A2 Type formula like below
=A1+1
use the Go to function press F5 or Ctrl G
in Reference type A10000
OK or Enter
press Ctrl Shift up array & finally
press Ctrl D