MathDB
2017 Theme #10

Source:

May 8, 2018
algebra

Problem Statement

Denote ϕ=5+12\phi=\frac{\sqrt{5}+1}{2} and consider the set of all finite binary strings without leading zeroes. Each string SS has a “base-ϕ\phi” value p(S)p(S). For example, p(1101)=ϕ3+ϕ2+1p(1101)=\phi^3+\phi^2+1. For any positive integer n, let f(n)f(n) be the number of such strings S that satisfy p(S)=ϕ48n1ϕ481p(S) =\frac{\phi^{48n}-1}{\phi^{48}-1}. The sequence of fractions f(n+1)f(n)\frac{f(n+1)}{f(n)} approaches a real number cc as nn goes to infinity. Determine the value of cc.