The table represents a quadratic function. Specifically, the output values correspond to the squares of the input values:
- \(1^2 = 1\)
- \(2^2 = 4\)
- \(3^2 = 9\)
- \(4^2 = 16\)
Thus, the relationship can be expressed as \(f(x) = x^2\), where the output is the square of the input.