afni.nimh.nih.gov

I tried it, and it works. Using count to generate 200 random numbers between 0 and 0 is a good trick. count is a small program that is useful for a lot of situations. 3dTcat is also more efficient in both performance and memory usage than 3dcalc. You can do this in a single line too:

3dTcat -prefix x4 x+orig."[`count -comma -dig 1 0 0 R4`]"