PERMUTATIONS - How to form permutations of n given things?

How to form permutations of n given things?								Counting permutations				no.of permutations		nPn=n!
1											1	1		1!
Insert new item first to the left of the previous permutations; and then shift its (new item's) place to the right by 1 position to get new permutations
2	1			i.e.	2	1					2 X 1	2		2!
2 shifts to the right by 1 position
	1	2			1	2
3 in left
3	2	1						2		3 x 2	3 x 2 x 1	6		3!
3	1	2
3 shifts to the right by 1 position
2	3	1						2
1	3	2
3 shifts to the right by 1 position
2	1	3						2
1	2	3
4 in the left most position
4	3	2	1					6		4 x 6	4 x 3 x 2 x 1	24		4!
4	3	1	2
4	2	3	1
4	1	3	2
4	2	1	3
4	1	2	3
4 shifts to the right by 1 position
3	4	2	1					6
3	4	1	2
2	4	3	1
1	4	3	2
2	4	1	3
1	4	2	3
4 shifts to the right by 1 position
3	2	4	1					6
3	1	4	2
2	3	4	1
1	3	4	2
2	1	4	3
1	2	4	3
4 shifts to the right by 1 position
3	2	1	4					6
3	1	2	4
2	3	1	4
1	3	2	4
2	1	3	4
1	2	3	4
and so on…..														5!