<p>In this article, we present a method to construct <i>e</i>-power <i>b</i>-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 <i>e</i> and base <i>b</i>, we consider happy numbers with at most <i>k</i> 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 <i>e</i>-power <i>b</i>-unhappy numbers of a given height.</p>

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A Tree Approach to the Happy Function

  • Eva G. Goedhart,
  • Yusuf Gurtas,
  • Pamela E. Harris

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.