I am not very good at these.....but here's ones for 2 and 3 and 4:
2 = \(\frac{4*4}{4+4}\)
3 = \(\sqrt{4}+\sqrt4-\frac44\)
4 = \(4! - 4*4 - 4\)
Also...what do you mean by concatenation?
I looked it up but I still don't really know what it is
*edit*
I accidentally put 5 fours for 2...thanks to geno for letting me know!! 
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