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S is a list with 50 numbers. If $$a_{n}= \frac{n+1}{n}-1$$ , where n is an odd number,and $$a_{n} = - a_{n-1}$$, where n is an even number, what is the range of the 50 numbers?
For any positive integer n, $$a_{n}= \frac{1}{n+1}- \frac{1}{n+3}$$

Quantity A

The sum of the first 10 terms

Quantity B

$$\frac{3}{4}$$


$$a_{1}=2$$,$$a_{2}=3$$,当n≥3时,$$a_{n} = a_{n-1} * a_{n-2}$$.What is the value of $$a_{8}$$?
The terms $$a_1, a_2, a_3,........a_n,.......$$ is defined by $$a_{1}=1$$, $$a_{n}=a_{n-1}+n$$ for all integers $$n \geq 2$$. What is the value of $$a_{49}$$?
How many different three-digit positive integers are there that are greater than 300 and contain three of the four digits 1, 2, 3, and 4?
S={1,2,3}
T={1,2,3,4}
Quantity A: The number of different four-digit integers formed by elements from Set S(all elements can be used by more than once)
Quantity B: The number of different three-digit integers formed by elements from Set T(all elements can be used by more than once)
Each digit of a four-digit integer is odd, how many such four-digit integers are there?
Rhonda has 4 different jackets, 3 different skirts, 2 different blouses,and 4 different scarfs that can be worn as part of an outfit. If an outfit consists of a jacket, a skirt, and a blouse with or without a scarf, how many different outfits can Rhonda wear?
In an election, 2 candidate, 3 candidates and 4 candidates campaign for A position, B position and C position, respectively. If every voter must choose one candidate for each position, how many different ways can a voter fill the voting ballot?
A 3-digit integer is formed by 3 different integers selected from 1,2,3,4,5. How many different such 3-digit integer?

There are 200 people, shown as the following graph. Now choose one person from each of sophomore,junior,senior to form a committee, how many combinations will there be?
n is the number of a 3-digit integer which has at least two "1"in its digits.

Quantity A

n

Quantity B

29


How many integers between 100 and 299 (inclusive) have a units digit between 3 and 9 (inclusive)?
Among the 300 students who sign up for a course, 9% are sophomore, 3% are junior and 1% is senior. If a teacher randomly selects 3 students form them, then how many different combinations of a sophomore student, a junior student and a senior student will be there?
In how many different ways can we use 0, 1, 2, 3, 4, to form a 4-digit number which must be a multiple of 3 (None of the five numbers can be used more than once)?
S={1, 2, 3, 4, 6}

T={1, 2, 3, 6, 8}

x is a number in set S, and y is a number in set T. What's the total number of all the different possible values of the product of x and y?
The hundreds digit and tens digit of a three-digit integer $$n$$ is odd and even,respectively. If the units digit is a number different from other two digits, what is the number of the possible value of $$n$$?
A 4-digit integer is formed by four integers selected from 0, 1, 2, 3 and the same figure can be repeatedly used. If the sum of the 4 digits is 3, how many different integers can be formed?
A 4-digit integer is formed by four integers selected from 0, 1, 2, 3, 4 and the same figure can be repeatedly used. If the sum of the 4 digits is 4, how many different integers can be formed?
Which of the following is a perfect square?

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