User blog comment:Katakana133/Well-defined Sam's Number./@comment-32783837-20180412235848

M1(n) = 1/H(n), where H(n) is the nth term of the harmonic number sequence.

It can be shown that M1(n) < 2n, making such a function very weak.

Also, S2(n) is not defined. If we say that Sk(n) = Mk(n), then S2(3) is infinity. Not a number.