MathDB
t = lim sum_{j=1}^N q^{n_j}.

Source: Polish MO Second Round 1974 p5

September 8, 2024
limitalgebraSequence

Problem Statement

The given numbers are real numbers q,t12;1) q,t \in \langle \frac{1}{2}; 1) , t(0;1 t \in (0; 1 \rangle . Prove that there is an increasing sequence of natural numbers nk {n_k} (k=1,2, k = 1,2, \ldots ) such that t=limNj=1Nqnj. t = \lim_{N\to \infty} \sum_{j=1}^N q^{n_j}.