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 Basic knowledge (Posted on 2006-01-10)
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.

 See The Solution Submitted by Alexis Rating: 5.0000 (1 votes)

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 Solution To Part II Comment 5 of 5 |
(In reply to Solution To Part I by K Sengupta)

General Rule For The Sequence

In the given problem, the n-1 term of the sequence is obtained by expressing n! in base n.

Accordingly,

The (2-1) th or the first term of the sequence is 10, which is
obtained by writing 2 in base 2 notation.

Similarly,

3rd term = 3! = 6 in base 3, which is 20 and so on.

The (10-1)th or 9th term of the sequence will this be obtained by
writing 10! =  3628800 in the base 10 or decimal notation, giving
3628800 as the required missing term.

Edited on April 18, 2008, 3:59 pm
 Posted by K Sengupta on 2008-04-18 15:58:14

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