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The sequence $10000, 121, 100, 31, 24, n, 20$ represents a number $x$ with respect to different bases. What is the missing number, $n$?

This is from my elementary computer aptitude paper. Is there any way to solve this quickly?

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    You can interpolate between $24$ and $20$ to obtain $22$. Is that the kind of trick you're looking for?2011-04-03
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    @Yuval Filmus:I don't get you .. could you please be more explicit?2011-04-03
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    Yuval and I are both assuming the bases are in ascending order with a difference of $1$. His interpolation is essentially an informal version of my answer. A little algebra beyond my answer shows the number is 16 and the bases are 2,3,4,5,6,?,82011-04-03

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