# Permutation for balls [duplicate]

Possible Duplicate:
number of combination in which no two red balls are adjacent.

We have $N$ slots. They have to be filled with balls (either green or red), one ball for each slot. Green balls can not be placed in consecutive slots. Find the number of different arrangements.

Can some one help?

• I have answered the question today on this site, for white and red, with no two red in a row. – André Nicolas Apr 28 '12 at 6:33
• Can you plz share the link..? – Muthukumar Apr 28 '12 at 6:34
• Here it is – André Nicolas Apr 28 '12 at 6:35

It might have been useful, and not difficult, to find the number of possibilities for $N=1$, $N=2$, $N=3$, and perhaps $N=4$.