Pattern Puzzles

Hard patterns bring in odd-one-out problems alongside trickier sequences. For odd-one-out: all the elements share a property except one. The property might be mathematical (all primes except one) or categorical (all five-letter words except one).

The sequences at this level tend to have non-obvious rules. You might need to look at second differences, check for Fibonacci-like recursion, or notice that the rule involves the position number itself (term 1 = 1², term 2 = 2², etc.). If brute-force checking doesn't work in 30 seconds, use a hint.