Question 158
On a blackboard a stranger writes the values of $s_{7}(n)^{2}$ for $n=0,1, \ldots, 7^{20}-1$, where $s_{7}(n)$ denotes the sum of digits of $n$ in base $7$. Compute the average value of all the numbers on the board.
MathNet 2017-part-07 — 172 problems (EN–VI) Question 158
Math Olympiad Vault · MathNet 2017-part-07 — 172 problems (EN–VI)