Folding a paper will make it thickness become double from it before. Unfolded paper has 1 thickness 1 times folded paper has 2 thickness 2 times folded paper has 4 thickness 3 times folded paper has 8 thickness
From here it is clear that the pattern is . SInce the paper is 0.1mm, then the function would be: f(n)= x 0.1mm