  Suppose that the moduli of the coefficients of a power series are 1/n!, while
the arguments are arbitrary. If an entire function f represented by such power
series decreases exponentially on some ray, then it has to be an exponential.
If the arguments of the coefficients are of the form 2pi n^2a, where a is
irrational, then the function displays the so-called "pits effect". More
precisely, under this condition, f is of completely regular growth with
constant indicator.
