Is it infinitely many?

Number Theory Level pending

1 , 101 , 10101 , 1010101 , 101010101 , {1, 101, 10101, 1010101, 101010101, ……}

How many number in the sequence above are primes?


The answer is 1.

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1 solution

Abdeslem Smahi
Jul 14, 2015

when we have an even number of 1 s 1's in any number of the sequence then the number is divisible by 101 101 it can be written as

if the number of 1 s 1's is odd so the number can be written as

so the only prime number is 101 101

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