How the solver works
The tool runs the same checks a person would, in the same order. It looks at the gaps between terms first, then at ratios, then at second-level gaps, then at the special families: squares, cubes, triangular numbers, primes and Fibonacci-style sums. Finally it tries the two patterns that catch most people out in aptitude tests: alternating operations and two interleaved sequences. Each rule it finds is stated in words with the working shown, so you can check it yourself rather than take the answer on trust.
When to trust the answer
Three terms can fit many rules. Four terms usually narrow it to one or two. If the solver lists more than one rule, the first is the simplest that fits, which is the convention aptitude tests follow. When a question gives you five or six terms and the solver still finds nothing, look for a pattern in the digits themselves (1, 11, 21, 1211 … is a description sequence) or a rule that depends on position (n² + n).
Learn the method
If you are preparing for a numerical reasoning test, the tool is most useful for checking your own working. The step-by-step method teaches the checklist so you can run it in your head in under thirty seconds, and Brisk’s daily brain teaser gives you two fresh sequences every day to practise on.
Common questions
What kinds of sequence can the solver recognise?
Constant, arithmetic (add or subtract), geometric (multiply or divide), quadratic and cubic (steadily changing gaps), Fibonacci-style sums, square, cube and triangular numbers, consecutive primes, multiply-then-add rules, gaps that multiply, alternating operations, and two interleaved arithmetic sequences.
Why does it show more than one rule?
Short sequences often fit several rules. 2, 4, 8 could be doubling or could be gaps that grow by 2. The solver lists every rule that fits all the numbers you gave, most likely first. Add one more term and the ambiguity usually disappears.
Does it work with negative numbers and decimals?
Yes. Type them as you would write them: -3, -1, 1, 3 or 0.5, 1, 2, 4.
Is anything I enter stored?
No. The solver runs entirely in your browser and nothing is sent to a server.