MathDB
Inductive 0/1 sequence

Source: 2017 Korea Winter Program Practice Test 2 #7

August 14, 2019
combinatorics

Problem Statement

For a number consists of 00 and 11, one can perform the following operation: change all 11 into 100100, all 00 into 11. For all nonnegative integer nn, let AnA_n be the number obtained by performing the operation nn times on 11(starts with 100,10011,10011100100,100,10011,10011100100,\dots), and ana_n be the nn-th digit(from the left side) of AnA_n. Prove or disprove that there exists a positive integer mm satisfies the following:
For every positive integer ll, there exists a positive integer kmk\le m satisfyingal+k+1=a1, al+k+2=a2, , al+k+2017=a2017a_{l+k+1}=a_1,\ a_{l+k+2}=a_2,\ \dots,\ a_{l+k+2017}=a_{2017}