  A bracket is a function that assigns a number to each monomial in variables
\tau_0, \tau_1, ... We show that any bracket satisfying the string and the
dilaton relations gives rise to a power series lying in the algebra A generated
by the series \sum n^{n-1} q^n/n! and \sum n^n q^n /n! .
  As a consequence, various series from A appear in the intersection theory of
moduli spaces of curves.
  A connection between the counting of ramified coverings of the sphere and the
intersection theory on moduli spaces allows us to prove that some natural
generating functions enumerating the ramified coverings lie, yet again, in A.
As an application, one can find the asymptotic of the number of such coverings
as the number of sheets tends to infinity.
  We believe that the leading terms of the asymptotics like that correspond to
observables in 2-dimensional gravity.
