An asymptotic Formula for the iterated exponential Bell Numbers

In 1938 E. T. Bell introduced “The Iterated Exponential Integers”. He proved that these numbers may be expressed by polynomials with rational coefficients. However, Bell gave no formulas for any of the coefficients except the trivial one, which is always 1. Our task has been to find the coefficient of the leading term, giving asymptotic information about these numbers.