MathDB
Girls in Math at Yale 2022 Problem 3: r/collaptzse

Source:

February 27, 2022
Yalecollege

Problem Statement

The Collaptz function is defined as C(n)={3n1n odd,n2n even.C(n) = \begin{cases} 3n - 1 & n\textrm{~odd}, \\ \frac{n}{2} & n\textrm{~even}.\end{cases} We obtain the Collaptz sequence of a number by repeatedly applying the Collaptz function to that number. For example, the Collaptz sequence of 1313 begins with 13,38,19,56,28,13, 38, 19, 56, 28, \cdots and so on. Find the sum of the three smallest positive integers nn whose Collaptz sequences do not contain 1,1, or in other words, do not collaptzse.
Proposed by Andrew Wu and Jason Wang