Let $B(n)$ be the smallest number larger than $n$ that can be formed by rearranging digits of $n$, or $0$ if no such number exists. For example, $B(245) = 254$ and $B(542) = 0$.
Define $\displaystyle T(N) = \sum_{n=1}^N B(n^2)$. You are given $T(10)=270$ and $T(100)=335316$.
Find $T(10^{16})$. Give your answer modulo $10^9 + 7$.
Solution
No solution yet. Write yours at
solutions/s925.md.