MathForces: Math Olympiads
MathForces - Math Olympiadsβeta
Login Register

Squared fours

Author: mathforces
Problem has been solved: 136 times

Русский язык | English Language



Consider a sequence $ a_n $ such that $ a_1 = 4 $ and $ a_n = 10a_ {n-1} + 4 $. Find the number of squares among the numbers $ a_1, a_2, ..., a_ {2020} $.





Sorry, you need to login into your account