Possible Duplicate:
In how many ways we can put $r$ distinct objects into $n$ baskets?
I have a doubt in following Combinatorics question : There are N bags, and there several balls of 4 colors (R,G,B,Y).Each bag should be filled by exactly one ball with the following condition -
-The color of ball in the consecutive bags must be different.
-The color of ball in first and last must be distinct too.
How many ways are there?
For N=2:
B-1|B-2 R G R B R Y G R G B G Y B R B G B Y Y R Y G Y B
For N=3
B-1 B-2 B-3 R G B R G Y R B G R B Y R Y G R Y B G R B G R Y G B R G B Y G Y R G Y B B R G B R Y B G R B G Y B Y R B Y G Y R G Y R B Y G R Y G B Y B R Y B G