## Zentralblatt MATH

Publications of (and about) Paul Erdös

Zbl.No:  401.10003
Autor:  Erdös, Paul; Szekeres, G.
Title:  Some number theoretic problems on binomial coefficients. (In English)
Source:  Aust. Math. Soc. Gaz. 5, 97-99 (1978).
Review:  In this paper some problems which are simple to state but probably difficult to solve are posed concerning binomial coefficients. Let P(m,n) denote the greatest prime factor of (m,n). Then the authors conjecture that if 1 \leq j \leq n/2 then P(\binom ni, \binom nj] \geq i with equality holding only in a few special cases (several of which are given). If f(n) = max1 < j \leq n/2(n,[\binom nj)) it is not difficult to show that f(n) \geq p(n) is the smallest prime factor of n, and that if n is not a prime power then f(n) \leq n/P(n) where P(n) is the greatest prime power which divides n. The authors remark that it would be of interest to characterize those n for which f(n) = n/P(n). (For example, f(30) = 6.) They also mention that it seems likely that f(n) > \sqrt n for infinitely many n.
Reviewer:  P.Hagis
Classif.:  * 11A05 Multiplicative structure of the integers
05A10 Combinatorial functions
11A41 Elemementary prime number theory
00A07 Problem books
Keywords:  binomial coefficients; prime factors

© European Mathematical Society & FIZ Karlsruhe & Springer-Verlag