Question

What is the rule for sequence 4,8,20,56,164

Answer 1

Answer:

Find the formula for the n-th term in the sequence: 4, 12, 20, 28, 36,...

To add from 4 to 12, I'd have to use 8. To add from 12 to 20, I'd also have to use 8. Let's check to see if "add 8" is the rule:

4 + 8 = 12

12 + 8 = 20

20 + 8 = 28

28 + 8 = 36

It appears that the rule is "add 8". So what is the rule for the n-th term? Let's look at the terms:

n = 1: 4

n = 2: 4 + 8

n = 3: 4 + 8 + 8 = 4 + 2×8

n = 4: 4 + 8 + 8 + 8 = 4 + 3×8

n = 5: 4 + 8 + 8 + 8 + 8 = 4 + 4×8

Following this pattern, the rule for the n-th term will be:

an = 4 + (n – 1)8

Answer 2

Answer:

the next one is 242

Step-by-step explanation:

4, 8, 20, 56, 164, 242