The TREE sequence is a fast-growing function arising out of graph theory, devised by mathematical logician Harvey Friedman. Friedman showed that the function eventually dominates all recursive functions provably total in the system \( ext{ACA}_0\)+\(\Pi_2^1\)-\( ext{BI}\). The smallest nontrivial member of the sequence is the famously large TREE(3), notable because it is a number that appears in serious mathematics that is larger than Graham's number.