Crackam
Crack the pattern. Predict what comes next.
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What number comes next?
Game over
How to play
Every puzzle hides a rule. Work it out, then fill the gap.
1. Compare each number with the one after it. Does it go up by the same amount? Get multiplied? Is each one the two before it added together?
2. Type your answer and press Enter, or tap Check. Press Enter again for the next question.
3. If two gaps are shown, give both numbers separated by a comma — like 23, 27.
4. Get it wrong and the working is shown underneath, so you can see the rule you missed.
5. Hint costs points: the first press names the pattern type, the second spells out the rule.
1. Compare each number with the one after it. Does it go up by the same amount? Get multiplied? Is each one the two before it added together?
2. Type your answer and press Enter, or tap Check. Press Enter again for the next question.
3. If two gaps are shown, give both numbers separated by a comma — like 23, 27.
4. Get it wrong and the working is shown underneath, so you can see the rule you missed.
5. Hint costs points: the first press names the pattern type, the second spells out the rule.
Get Crackam on your phone
It installs straight from this page — no app store, nothing to download, and it
works with no internet once it is on your device.
iPhone & iPad — tap the Share button (the square with an arrow pointing up), scroll down and tap Add to Home Screen.
Works in Safari, and in Chrome on iOS 16.4 or later. If you cannot find the option, open the page in Safari.
Android — tap the ⋮ menu in Chrome, then Install app (sometimes shown as Add to Home screen).
Windows — in Chrome or Edge, click the small install icon in the address bar, or open the browser menu and choose Install Crackam.
Mac — in Safari, choose File → Add to Dock.
Once installed it opens full screen with its own icon, and your scores are kept on your own device.
iPhone & iPad — tap the Share button (the square with an arrow pointing up), scroll down and tap Add to Home Screen.
Works in Safari, and in Chrome on iOS 16.4 or later. If you cannot find the option, open the page in Safari.
Android — tap the ⋮ menu in Chrome, then Install app (sometimes shown as Add to Home screen).
Windows — in Chrome or Edge, click the small install icon in the address bar, or open the browser menu and choose Install Crackam.
Mac — in Safari, choose File → Add to Dock.
Once installed it opens full screen with its own icon, and your scores are kept on your own device.
The patterns you'll meet
Arithmetic — the same amount is added or subtracted each time. 4, 9, 14, 19…
Geometric — each term is multiplied by the same number. 3, 6, 12, 24…
Growing steps — the gaps themselves grow evenly. 2, 5, 10, 17… (+3, +5, +7)
Sum of the last two — Fibonacci style. 2, 3, 5, 8, 13…
Square & triangle numbers — 1, 4, 9, 16… and 1, 3, 6, 10…
Two series braided — alternate terms belong to different runs. 2, 100, 5, 90, 8, 80…
Alternating steps — add, then multiply, then add again. 3, 8, 16, 21, 42…
Easy uses arithmetic only. Medium adds multiplying, growing steps and square numbers. Hard can throw any of them at you — so the first job becomes working out which kind it is.
Geometric — each term is multiplied by the same number. 3, 6, 12, 24…
Growing steps — the gaps themselves grow evenly. 2, 5, 10, 17… (+3, +5, +7)
Sum of the last two — Fibonacci style. 2, 3, 5, 8, 13…
Square & triangle numbers — 1, 4, 9, 16… and 1, 3, 6, 10…
Two series braided — alternate terms belong to different runs. 2, 100, 5, 90, 8, 80…
Alternating steps — add, then multiply, then add again. 3, 8, 16, 21, 42…
Easy uses arithmetic only. Medium adds multiplying, growing steps and square numbers. Hard can throw any of them at you — so the first job becomes working out which kind it is.
About Crackam
Crackam takes its name from Nigerian Pidgin — crack am, meaning solve it. That is the whole game in two words.Each round shows part of a number series with a number missing, and you work out the rule that produces it — a constant step, a multiplier, growing gaps, a Fibonacci-style sum, square or triangle numbers, or two sequences braided together. Number pattern questions like these turn up throughout maths lessons and in the reasoning sections of aptitude, entrance and graduate-trainee tests, so it doubles as practice. Wrong answers show the full working, which makes it a way to learn the patterns rather than just be scored on them.
It runs in any modern browser on a phone, tablet or computer. There is nothing to download, no account, no ads and no tracking — and once it has loaded once, it keeps working with no internet connection at all.