The sequence presented in the image is:

$1, 3, 4, 7, 11, 18, \_$

To find the number that should replace the blank, let's analyze the differences between consecutive terms:

$3 - 1 = 2$ $4 - 3 = 1$ $7 - 4 = 3$ $11 - 7 = 4$ $18 - 11 = 7$

The differences are: $2, 1, 3, 4, 7$

It seems that the differences follow a pattern that alternates and increases in an irregular manner. To continue this, the next difference would be $7 + 1 = 8$.

So, the next number in the sequence is: $18 + 8 = 26$

Thus, the number that should replace the blank is 26.

Would you like a more detailed explanation or have any questions?

Here are 5 related questions:

1. How do you find the next term in an arithmetic sequence?
2. What is the difference between arithmetic and geometric sequences?
3. Can you identify patterns in more complex sequences?
4. How would you extend this sequence by two more terms?
5. Are there any specific types of number sequences that follow irregular differences like this?

Tip: When analyzing a number sequence, checking the differences between consecutive terms can often help you identify the pattern!