Prime & Modular Anomaly
Terms follow a hidden membership rule: all prime, all square numbers, Fibonacci, or a cyclic pattern.
Prime & Modular Anomaly sequences are the fallback when nothing else works. They appear in all three major Dutch assessment providers and are designed to test whether you can step back and look for a mathematical property rather than an additive or multiplicative rule. The most common variants in SHL Verify G+ and Cubiks Logiks are sequences of consecutive prime numbers, perfect squares, and Fibonacci numbers. Modular cycling sequences (where terms repeat with a fixed period) appear less frequently but are distinctive once recognised.
How to solve it
- 1Exhaust the standard checks first: test differences, ratios, alternating patterns. If nothing fits, switch to property checking.
- 2Test for primes: is each term a prime number? Primes to know: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47.
- 3Test for perfect squares: 1, 4, 9, 16, 25, 36, 49, 64, 81, 100... Are all terms on this list?
- 4Test for Fibonacci: does each term equal the sum of the two terms before it?
- 5Test for a cyclic pattern: list the remainders when dividing each term by 2, 3, or 4. If they repeat, you have a modular sequence.
Worked examples
Example 1
Consecutive primes
Rule: Consecutive prime numbers
Example 2
Perfect squares
Rule: 1², 2², 3², 4², 5², 6²
Example 3
Fibonacci sequence
Rule: Each term = sum of the two before it
Common mistakes
- Spending too long on differences and ratios. If neither approach shows a clear pattern after 20 seconds, switch to property checking immediately.
- Not knowing the first 15 primes from memory. In a timed test, looking them up costs too much time. Memorise: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47.
- Confusing perfect squares with Fibonacci. Squares grow much faster; Fibonacci differences also follow the Fibonacci pattern.
Ready to practice?
Work through timed Prime & Modular Anomaly questions and track your accuracy.