1. What is the general term formula for 3; 5; 11; 21; 43; 85; 171?

The general term formula is: an + 2 = 2An + 1 + an-2an-1, where n ≥ 2, N + 2, N + 1, N, n-1 are subscripts. The solution is to let A1 = 1, A2 = 3, A3 = 5, A4 = 11, A5 = 21, A6 = 43, A7 = 85, a8 = 171, (A1 represents the first term in the sequence, 1 is subscript, the numbers next to B and C also represent subscript, and so on) and then let B1 =

RELATED INFORMATIONS

1. The law of exploration: 1,3,5,11,21, (), (), 171341
2. The combination of interval sequence and equal difference equal ratio mixed sequence, such as: 3,1,5,1,11,1,21,1, (43) How to solve it?
3. 3,11,43171683... Is there an analytic expression for this sequence? Wrong. It's the general formula!
4. Find sequence 3 / 1 * (2 ^ 2), 5 / (2 ^ 2) * (3 ^ 2), 7 / (3 ^ 2) * (4 ^ 2) The sum of the first n terms of (2n + 1) / A ^ 2 (n + 1) ^ 2
5. The number of terms of sequence 5,7,9,11,..., 2N-1 is
6. The number of items of 9.11.13.2n-1 is 1. The number of items of 9.11.13... 2N-1 is
7. The number of terms of sequence 3,5,9,11..., 2n + 1
8. How to find the number of items in a sequence? For example, how to find the number of items in a sequence an = (2n + 1) + (2n-1) + (2n-2) +. + 7 + 5 + 1 There is also a general way to find the number of items in a sequence I'm in the third year of senior high school now. I'm going through the first round of review to find out how to learn
9. What is the number of terms of the sequence 1 + 3 + 5 +. + (2n-1)? How to calculate it?
10. If 2 and 8 / 21 divided by M = 2 and 1 / 2, then m * 7 / 20=____
11. Sequence √ 3, 3, √ 15 ,√3（2n-1),…… What is 9?
12. Known finite sequence 5,7,9 , 2n + 7 (n is an even number), then 9 + n is the item of the sequence The answer is n / 2 + 3,
13. Judge whether 9 is the item in sequence 3 [2n-7]. If so, please indicate which item is it
14. Known sequence 3, 9, 15 ，3（2n-1），… So what is 81 () A. 12B. 13C. 14D. 15
15. Given the arithmetic sequence 3.7.11.15.195, how many items are there in this sequence
16. Given the sequence √ 3, √ 7, √ 11, √ 15,., then 5 √ 3 is its number one?
17. (1 + 2 + 3 + 4 +. 2n) / 1 + 3 + 5 + 7 +. 2N-1 = 21 / 10
18. Given 8 ^ m = 12,4 ^ n = 6, find the value of 2 ^ (6m-2n + 1)
19. Given 8 ^ m = 3,4 ^ n = 6, find the value of 2 ^ 6m + 2n + 1
20. Given that the general term formula of the sequence {an} is an = n / N ^ 2 + 156 (n belongs to positive integer), what is the maximum term of the sequence