Wrong Number

One number breaks the hidden rule — spot it.

How to play

Every number in the sequence except one follows a hidden rule. Find the rule, then identify the single number that breaks it.

• Most of the sequence follows a consistent pattern — only one entry is the outlier.
• Test the rule against several consecutive numbers before deciding which one is wrong.
• No paper or calculator — do it in your head.
• Difficulty ramps up automatically as you answer correctly.

Why this matters

Spotting the outlier requires holding a rule in mind while checking it against every item — a working-memory-heavy variant of the pattern-detection tasks used in WISC's Fluid Reasoning index for school-age children. Read more about the Wechsler Intelligence Scale for Children (WISC).

This game trains