MathDB
Putnam 1980 B6

Source: Putnam 1980

April 1, 2022
Putnam

Problem Statement

An infinite array of rational numbers G(d,n)G(d, n) is defined for integers dd and n n with 1dn1\leq d \leq n as follows: G(1,n)=1n,      G(d,n)=dni=dnG(d1,i1)  for  d>1.G(1, n)= \frac{1}{n}, \;\;\; G(d,n)= \frac{d}{n} \sum_{i=d}^{n} G(d-1, i-1) \; \text{for} \; d>1. For 1<d<p1 < d < p and pp prime, prove that G(d,p)G(d, p) is expressible as a quotient s\slash t of integers ss and tt with tt not divisible by p.p.