In the arithmetic sequence an, A2 = 4, A6 = 12, then the sum of the first n terms of the sequence an / 2 ^ (n + 1) is equal to

In the arithmetic sequence an, A2 = 4, A6 = 12, then the sum of the first n terms of the sequence an / 2 ^ (n + 1) is equal to

A2 = 4, A6 = 12 can be calculated
a1=2,d=2
an=2n
Let BN = an / 2 ^ (n + 1) = n / 2 ^ n
Sn=1/2+2/2^2+3/2^3.+n/2^n
1/2*Sn=1/2^2+2/2^3+3/2^4.+n/2^(n+1)
Sn-1/2Sn=1/2+1/2^2+1/2^3.+1/2^n-n/2^(n+1)
1/2Sn=1-(1/2)^n-n/2^(n+1)
Sn=2-(1/2)^(n-1)-n/2^n

In an arithmetic sequence with a positive first term, the sum of the first three terms is equal to the sum of the first 11 terms. When the sum of the first n terms of the sequence is the largest, n is equal to ()
A. 5B. 6C. 7D. 8

According to the meaning of the problem, the sequence decreases monotonously, and the tolerance D is less than 0. Because S3 = S11 = S3 + A4 + A5 + +A10 + a11 so A4 + A5 + +a7+a8+… +A10 + a11 = 0, that is, A4 + a11 = A7 + A8 = 0, so when n = 7, a7 > 0, a8 < 0

Fill in the blanks with the law of periodic sequence
1. 3、 1、 1、 4、 3、 3、 4、( )
A.1 B.2 C.3 D.4

Choose C to add these numbers, 3 + 1 equals 4, 1 + 4 equals 5, 3 + 3 equals 6, then the last number should be 3, 4 + 3 equals 7

What is the law of 0 2 / 3 4 15 / 2 () sequence

0 6 24 45 ?1 4 9 16 25 491 2 3 4 51 8 27 64 125-1 -2 -3 -4 -50 6 24 60 120a(n-1)(n-2)(n-3),n=4a*3*2*1=15a=2.5120-2.5*4*3*2=120-60=600 6 24 45 600 2/3 4 15/2 10

What's the law of this sequence

The product of two arithmetic sequences
1=1*1
6=2*3
15=3*5
28=4*7

-What's the rule of 2, - 8,0,64?

The answer is - 64
-2,-8,0,64
0 = (-2)^3 - (-8)
64 = (-8)^2 - 0
-64 = 0^1 - 64

Sequence - 1,0,1,8, (), 64,

27
They are the third power of - 10 1 2 3 4

-2 - 8 064 () sequence

The number sequence - 2. - 8.0.64 can be changed into: 1 * (- 2). 8 * (- 1). X * 0.64 * 1. We know that it is the number of items in a column multiplied by the natural number starting from (- 2). We get a new number sequence: 1.8. X.64. The transformation is 2 ^ 0.2 ^ 3. X.2 ^ 6. The coefficient is 0.3. A.6

The nth number of 2,7,12,17,22... () in the sequence, the sequence rule: 1,8,27,64, ()... ()
① The nth number of 2,7,12,17,22... () in the sequence, the sequence rule: 1,8,27,64, ()... () n numbers
② The first number is 3 = 2 + 1, the second number is 5 = 3 + 2, the third number is 9 = 5 + 4, and the fourth number is 17 = 9 + 8

2,7,12,17,22,27,32,37,42,47. The odd bit is 10 more than the last odd bit, and the even bit is 10 more than the last even bit. The nth number: when n is odd, it is 5 (n-1) + 2 = 5n-3; when n is even, it is 5n-10 + 7 = 5n-3. So whether n is odd or even, the nth number is 5n-31,8,27,64125

There is a series of numbers 1, - 1,2, - 1,2, - 3,1, - 2,3, - 4. According to this law, the hundredth number is

Without looking at the symbols, it is easy to find that the sequence is 1,1,2,1,2,3,1,2,3,4
So first of all, what is the absolute value of the hundredth number
Add 13 from 1 to 91, that is, the hundredth number is in the block of 1,2,3.14
You can count to 100th with your fingers. The absolute value is 9
Looking at the whole sequence, we find that the odd number is positive and the even number is negative
So the hundredth number is - 9