A Tree Approach to the Happy Function
摘要
In this article, we present a method to construct e-power b-happy numbers of any height. Using this method, we construct a tree that encodes these happy numbers, their heights, and their ancestry—relation to other happy numbers. For fixed power e and base b, we consider happy numbers with at most k digits and we give a formula for the cardinality of the preimage of a single iteration of the happy function. We show that these happy numbers arise naturally as children of a given vertex in the tree. We conclude by applying this technique to e-power b-unhappy numbers of a given height.