Two steps forward and one step back

Python 2, 18 bytes

lambda n:3*n-1%n*4

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I picked this trick up from xnor just a few days ago…!

Python 2, 20 bytes

lambda n:n*3-4*(n>1)

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Python 2, 17 bytes

lambda n:n-3%~n*2

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I found the expression by brute-force search. It effectively computes n+2*abs(n-2).