The best way to count by fours. If you count by fours you can go to twenty without using other numbers. In the sequence of four, eight, 12, 16, and 20. Sequence counting allows you to follow a pattern to reach the next logical number.
(4!/4)4 - 4
4+4(4-4)
4*4*4-(4/4)
(4x4+4)/4
4/4+4/4=2
4! + [(4*4)/4^2]
4 + 4 - (4/4) = 7
4/4+4/-4
(4+4)/4 + 4 =6
-4-4+4/4
(4*4)-(4/4)