In each number except 383, the product of first and third digits is the middle one.

In each number except 751, the difference of third and first digit is the middle one.

Each of the numbers except 23, is perfect square.

The pattern is 1², 2², 3², 4², 5², 6², 7². But, instead of 5², it is 20 which to be turned out.

Each of the numbers except 81 is a prime number.

Each of the numbers is a prime number except 12.

(1×1) + 1, (2×2) + 1, (3×3) + 1, (4×4) + 1, (5×5) + 1, (6×6) + 1, (7×7) + 1, (8×8) + 1
But, 64 is out of pattern.

Each of the numbers except 21 is an even number.

Each of the numbers except 72 is a perfect square.