Difference between revisions of "2004 AMC 10A Problems/Problem 24"
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Let <math>a_1,a_2,\cdots</math>, be a [[sequence]] with the following properties. | Let <math>a_1,a_2,\cdots</math>, be a [[sequence]] with the following properties. | ||
− | + | :(i) <math>a_1=1</math>, and | |
− | + | :(ii) <math>a_{2n}=n\cdot a_n</math> for any [[positive integer]] <math>n</math>. | |
What is the value of <math>a_{2^{100}}</math>? | What is the value of <math>a_{2^{100}}</math>? |
Revision as of 16:31, 6 February 2007
Problem
Let , be a sequence with the following properties.
- (i) , and
- (ii) for any positive integer .
What is the value of ?
Solution
Note that
so that
where in the last steps we use the exponent rule and the formula for the sum of an arithmetic series.
See also
2004 AMC 10A (Problems • Answer Key • Resources) | ||
Preceded by Problem 23 |
Followed by Problem 25 | |
1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25 | ||
All AMC 10 Problems and Solutions |