MathDB

1...1 2 1...1 is a prime

Source: Germany Federal - Bundeswettbewerb Mathematik 2010, round 1, p1

April 9, 2020

number theoryprime numbersDigits

Problem Statement

Exists a positive integer

n

such that the number

\underbrace{1...1}_{n \,ones} 2 \underbrace{1...1}_{n \, ones}

is a prime number?