Find the rule: 1.3.5.11.21. (). (). 171.341

Find the rule: 1.3.5.11.21. (). (). 171.341

1×2+3=5
3×2+5=11
5×2+11=21
11×2+21=43
21×2+43=85
43×2+85=171
85×2+171=341

11 32 21 31 22 12 () () find the law

It should be 33, 22, 32 and 23. You can subtract 1 and 62 and 7.12 in order. 11 is 1, and 33 minus 32 is 1

The nth number of 3,7,11,15,19

The nth number is "n + 4"

Observe the order of the following numbers, and then fill in the appropriate number on the line; 3, - 7,11, - 15,19, - 23,27 The nth number is
Then why don't I take the numbers in

Without looking at the symbols, we can see that each term is added with 4,7 = 3 + 4,11 = 7 + 4
So the nth term is 3 + (n-1) * 4 = 4N-1
Look at the sign again, the odd term is positive, the even term is negative, so multiply by (- 1) ^ (n + 1)
So the nth number is (4N-1) * (- 1) ^ (n + 1)
^On the left is the base, and on the right is the exponent (- 1) ^ (n + 1), which is the power of - 1 to the power of N + 1