The number of regular columns: 2, 5, 9, 14, 20, 27 The 2011 number in this column is______ .

The number of regular columns: 2, 5, 9, 14, 20, 27 The 2011 number in this column is______ .

Item 2011 is:
2+3+4+… +2012，
=（2+2012）×2011÷2，
=2014×2011÷2，
=2025077；
So the answer is: 2025077

The number of columns arranged according to the rule: 2,5,9,14,20,27 What is the 2005 number of this column? Write out the calculation process

Call this sequence a
The first term A1 = 2, then A2 = 5
an=a(n-1)+n+1.
So an is the sum of arithmetic sequence, (2 + (n + 1)) * (n) / 2
a2005=(2005+3)*2005/2=2013020

There is a column of numbers, arranged according to a certain rule into 1, - 3, 9, - 27, 81, - 243... What are the three adjacent numbers? What are the three numbers

A sequence of numbers equal to - 3
If the first number is x, then the last two numbers are - 3x, 9x,
x+(-3)x+9x=2009
7x=2009
x=287
The triple number is 287, - 8612583
But it's obviously not in the sequence

What is the tenth number in this sequence, the number of the 100th number and the nth number

The first number is 5 and then 3
The first item is 5 and the tolerance is 3
General term formula 5 + 3 × (n-1) = 3N + 2

The number in the order of 1 / 2, - 1 / 5,1 / 10, - 1 / 17,1 / 26, - 1 / 37?

The denominators differ in sequence by 3,5,7,9
The odd number term is positive and even number term is negative
So the tenth number is - 1 / 101

Observe the following column numbers: 1 / 2 - 1 / 6 1 / 12 - 1 / 20... Norn is an integer greater than 1. Write the nth number according to the above arrangement

Hello! When n is odd, the nth number is 1 / N * (n + 1) when n is even, the nth number is - 1 / N * (n + 1)

The number of regularly arranged columns: 2, 4, 6, 8, 10, 12 Each term is represented by the formula 2n (n is a positive integer). The number of regularly arranged columns: 1, - 2, 3, - 4, 5, - 6, 7, - 8 (1) What formula do you think can be used to express each term; (2) What is its 100th number? (3) Is 2006 the number in this column? If so, what is the number?

(1) Each of its terms can be expressed by the formula (- 1) n + 1n (n is a positive integer)
(2) Its 100th number is - 100
(3) 2006 is not a number in this column because even numbers in this column are all negative
When n is odd, it is expressed as n. when n is even, it is expressed as - n

There is a column of numbers arranged according to a certain rule as 1, - 3,5, - 7,9 If the sum of three adjacent numbers is - 201, find the three numbers?

Let one of the three numbers be X
（-x-2）+x+（-x+2）=-201，
The solution is: x = 201,
∴-x+2=-199，-x-2=-203，
A: these three numbers are - 199, 201 and - 203

1. There are some numbers arranged according to a certain rule: 1, - 3,5, - 7,9 If the sum of three adjacent numbers is - 201, find the three numbers 2. Party A and Party B are on the same road in the same direction. Party A travels 3 km / h and B 5 km / h. Party A passes through place a at 12:00 noon and passes through place a at 2:00 pm. What time can party B catch up with Party A?

1. The law is: [(- 1) ^ (n + 1)] × (2n + 1), and the sum of the two numbers before and after each number is equal to - 2 times of the middle number, and the sum of three adjacent numbers is - 201, then the middle number is - 201 / (- 2 + 1) = 201, the former number is - 199, the latter number is - 203

The last three numbers of a column arranged in order: 1, - 3,5, - 7,9 are given

-The following number 2000 is - 3999
A group of numbers 1, - 3,5, - 7,9 are given Please write the seventh number 13 according to the rule
Thirteen
The nth number is (- 1) n + 1 (2n-1)
（-1）n+1（2n-1）
.