R, 37 35 bytes

Nothing original, given the previous answers:

(((3+5^.5)/2)^(scan()+1)/5)%/%1*4+2 

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R, 37 35 31 bytes

Nothing original, given the previous answers:

(((3+5^.5)/2)^(scan()+1)/5)%/%1*4+2 

was 35 bytes, but Guiseppe got rid of four parentheses

((3+5^.5)/2)^(scan()+1)%/%5*4+2 

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R, 37 bytes

Nothing original, given the previous answers:

n=scan()+1;(((3+5^.5)/2)^n/5)%/%1*4+2 

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R, 37 35 bytes

Nothing original, given the previous answers:

(((3+5^.5)/2)^(scan()+1)/5)%/%1*4+2 

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