Question 16
Starting with $37$, successively prefix the digit $5$ to obtain
$37$, $537$, $5537$, $55537$, $555537$, ...
How many terms are prime?
$37$, $537$, $5537$, $55537$, $555537$, ...
How many terms are prime?
MathNet 2013 Question 16
Math Olympiad Vault · MathNet 2013