Find the Next Number After 2, 3, 5, 9, 17
This page contains Coupang Partners affiliate links; the operator may earn a commission.
Key Takeaway
Yesterday's Quiz 3 answer is ② ■■. Today's Quiz 4 is a sequence puzzle: what comes after 2, 3, 5, 9, 17? Look for a rule that builds each number from the one before it. Today's answer goes up tomorrow in Quiz 5.
What was yesterday's answer?
Quiz 3 was a shape pattern puzzle about filling the empty cell in a 3×3 grid. The answer is ② ■■.
- Type of shape: each row uses one kind, ● in row 1, ▲ in row 2, and ■ in row 3. That rules out ④ ▲▲.
- Number of shapes: each row and each column holds the groups of 1, 2, and 3 shapes exactly once.
| Column 1 | Column 2 | Column 3 | |
|---|---|---|---|
| Row 1 count | 1 | 2 | 3 |
| Row 2 count | 2 | 3 | 1 |
| Row 3 count | 3 | 1 | 2 |
Row 3 already has 3 and 1, and column 3 also has 3 and 1, so the one left is 2.
What is today's puzzle?
| Position | 1 | 2 | 3 | 4 | 5 | 6 |
|---|---|---|---|---|---|---|
| Number | 2 | 3 | 5 | 9 | 17 | ? |
- Difficulty: ★★☆☆☆
- Suggested time: 3 minutes
- Condition: every number is built from the single number right before it
Where should you start?
As in Quiz 1, start by writing the differences between neighboring numbers. If you see a familiar pattern in the line of differences, follow the rule from there. Another approach is to multiply each number by the same amount and then subtract something.
When can you check the answer?
The answer and explanation go up tomorrow (October 17) morning, at the very top of the Quiz 5 post. It will also show that two different methods lead to the same answer.
Is there a quick order for tackling sequences?
Sequences go faster if you check in this order: differences, ratios (how many times larger), then the sum of the previous two numbers. If the differences are not steady, look at the differences of the differences, or the ratios between them. It is practice in spotting a rule quickly, like the pattern recognition item in the online brain test Mensa Korea describes (checked 2026-10-13). It is a practice puzzle, separate from the approved intelligence test and top 2% score that Mensa uses as its membership standard.
| Order to check | What to look at | Example |
|---|---|---|
| 1 | Differences between neighbors | Quiz 1 |
| 2 | How many times larger each term is | 2, 4, 8, 16 |
| 3 | Sum of the previous two numbers | 1, 1, 2, 3, 5 |
Frequently Asked Questions
What is the answer to Quiz 3?
② ■■. Each row and each column holds the groups of 1, 2, and 3 shapes exactly once.
When does the Quiz 4 answer come out?
It goes up with the explanation at the very top of the Quiz 5 post, published the next day.
Can I solve it using only the differences?
Yes. Writing out the differences can lead you to the same answer from a different direction.
Sources & Verification Date
- Mensa International membership requirements guide · Verified
- Mensa Korea online brain test introduction · Verified
All materials have been verified from official announcements and may have changed since verification.