Consider the given equation,
R2=6k
Put, k=0,1,2,3,......
Put,k=0 we get
R=0
Again put, k=1we get,
R2=6×1
R=√6=2.448489..=2.448
Again put k=2 we get,
R2=6×2
R=2√3
Hence, this is the answer.