P294
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Sum of Digits - Experience #23

ℹ️Published on Saturday, 29th May 2010, 09:00 am; Solved by 1044;
Difficulty rating: 45%

For a positive integer $k$, define $d(k)$ as the sum of the digits of $k$ in its usual decimal representation. Thus $d(42) = 4+2 = 6$.

For a positive integer $n$, define $S(n)$ as the number of positive integers $k \lt 10^n$ with the following properties :

  • $k$ is divisible by $23$ and
  • $d(k) = 23$.
You are given that $S(9) = 263626$ and $S(42) = 6377168878570056$.

Find $S(11^{12})$ and give your answer mod $10^9$.



Soluzione

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