IMO Shortlist 1999 problem N6
Dodao/la: arhiva2. travnja 2012.
Prove that for every real number
there exists an infinite arithmetic progression such that:
- each term is a positive integer and the common difference is not divisible by 10
- the sum of the digits of each term (in decimal representation) exceeds
Izvor: Međunarodna matematička olimpijada, shortlist 1999