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jmc

number theory senior

Problem

A certain integer has digits when written in base . The same integer has digits when written in base . What is the sum of all possible values of ?
Solution
The smallest integer that has digits in base is , which stands for . The largest integer that has digits in base is , which is less than and therefore stands for .

Thus, when a -digit base- integer is written in base , its highest place value is either , , or . It follows that the base- expression has , , or digits, so the sum of all possible values for is .
Final answer
33