 As Turing said, “it is almost equally easy to define and investigate computable functions”: there is, in a certain sense, little difference between a computable number and a computable function. For example, the computable number .14159… (formed of the digits following the decimal point in π, 3.1419…) corresponds to the computable function: \(f(1) = 1\), \(f(2) = 4\), \(f(3) = 1\), \(f(4) = 5\), \(f(6) = 9\), … .