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OlympiadBench / 2000 / Find all positive integers n≥2 for which there exist n real…

Problem

Answer published by the source. Consult the official source to check your work against its answer.

question

Find all positive integers n2n \geqslant 2 for which there exist nn real numbers a1<<ana_{1}<\cdots<a_{n} and a real number r>0r>0 such that the 12n(n1)\frac{1}{2} n(n-1) differences ajaia_{j}-a_{i} for 1i<jn1 \leqslant i<j \leqslant n are equal, in some order, to the numbers r1,r2,,r12n(n1)r^{1}, r^{2}, \ldots, r^{\frac{1}{2} n(n-1)}.
Plain-text mathematical notation (without MathML)
Find all positive integers n≥2 for which there exist n real numbers a₁<⋯<a_(n) and a real number r>0 such that the (1)/(2)n(n−1) differences a_(j)−a_(i) for 1≤i<j≤n are equal, in some order, to the numbers r¹,r²,…,r^((1)/(2)n(n−1)).
Original LaTeX notation
Find all positive integers $n \geqslant 2$ for which there exist $n$ real numbers $a_{1}<\cdots<a_{n}$ and a real number $r>0$ such that the $\frac{1}{2} n(n-1)$ differences $a_{j}-a_{i}$ for $1 \leqslant i<j \leqslant n$ are equal, in some order, to the numbers $r^{1}, r^{2}, \ldots, r^{\frac{1}{2} n(n-1)}$.

answer type

Numerical

is multiple answer

true

language

English

question type

Open-ended

subject

Math

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Source and history

Official source

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