Answer: What Comes Next? #401

The answer is C: 13.

The rule

Each number is the two numbers before it added together. 1 + 1 = 2, 1 + 2 = 3, and so on. The famous Fibonacci sequence works like this, starting 1, 1, 2, 3, 5, 8.

The pattern as Python code

Here is a tiny Python program that follows the same rule. Type it into IDLE and run it to print the whole pattern, including the answer.

a, b = 1, 1
for step in range(7):
    print(a)
    a, b = b, a + b

When you run it, Python prints:

1
1
2
3
5
8
13