In the early 1970s David Klarner and Richard Rado studied integer orbits of semigroups
of such affine functions in an arbitrary number of variables, motivated by work
of Crampin and Hilton on self-orthogonal Latin squares described below. In response
to a question they posed about a particular example, Paul Erd˝os proved a theorem on
the size of an orbit for certain semigroups of univariate functions, upper bounding the
number of integers below a given cutoff T occurring in such orbits, cf. [37, Theorem
8]. Erd˝os’s interest in this orbit problem led him to offer a reward for a particular semigroup
iteration problem. This problem was solved by Crampin and Hilton in 1972, but
their solution was never published. We supply a reconstructed solution here.