The McCarthy-91 function is the recursive function defined for positive integer n by M(n) = {M(M(n + 11)) | for n<=100 n - 10 | for n>100. auto right match It takes the value 91 for all n = 1, 2, ..., 101, and then continues 92, 93, 94, ... (OEIS A103847). It was invented by computer scientist J. McCarthy.