2016/11/24 by Nathan Fox, Fox, Nathan
Computer Science · Engineering · Mathematics · #Coding theory and cryptography #graph theory and CDMA systems #Analytic Number Theory Research
paper · pdf · doi:10.48550/arxiv.1611.08244
Hofstadter's Q-sequence remains an enigma fifty years after its introduction. Initially, the terms of the sequence increase monotonically by 0 or 1 at a time. But, Q(12)=8 while Q(11)=6, and monotonicity fails shortly thereafter. In this paper, we add a third term to Hofstadter's recurrence, giving the recurrence B(n)=B(n-B(n-1))+B(n-B(n-2))+B(n-B(n-3)). We show that this recurrence, along with a suitable initial condition that naturally generalizes Hofstadter's initial condition, generates a sequence whose terms all increase monotonically by 0 or 1 at a time. Furthermore, we give a complete description of the resulting frequency sequence, which allows the nth term of our sequence to be efficiently computed. We conclude by showing that our sequence cannot be easily generalized.