Prove that there are infinitely many terms of the arithmetic sequence which are of the form . In other words a number that is made up using only the digit .
(Hint: )
Prove that there are infinitely many terms of the arithmetic sequence which are of the form . In other words a number that is made up using only the digit .
(Hint: )
Note that and therefore is in the arithmetic sequence. Furthermore, is divisible by and hence is in the sequence, since
In fact, any number consisting of s will be one more than a multiple of , since the number consisting of s will be a multiple of and hence a multiple of . Thus there are infinitely many terms in the sequence that only uses the digit .