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Basic knowledge (Posted on 2006-01-10) |
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What is the next number in this sequence?
10, 20, 120, 440, 3200, 20460, 116600, 612700...
What is the general rule behind the sequence?
Hint: This sequence starts in n=2. A computer will probably not be able to solve it, but you're welcome to try.
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Submitted by Alexis
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Rating: 5.0000 (1 votes)
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Solution:
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The next number in the sequence is 3628800.
The general rule behind the sequence is to write n! in base n.
For the first number, 2!=2, written in base 2 (binary) is 10.
For the second number, 3!=6, written in base 3 would be 20 (2*3^1 + 0*3^0).
For the third number, 4!=24, written in base 4 would be 120 (1*4^2 + 2*4^1 + 0*4^0).
For the last number (the ninth number), 10!=3628800, which written in base 10 is the same number.
Therefore, the answer is 3628800, or 10!.
If anyone wants to try with a computer, please post the solution you find. I think it would be interesting to see how a computer simulates human intuition. |
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