The subcubic graph numbers are the outputs of a fast-growing combinatorial function. They were devised by Harvey Friedman, who showed that it eventually dominates every recursive function provably total in the theory of \(\Pi^1_1\)-\( ext{CA}_0\), and is itself provably total in the theory of \(\Pi_1^1- ext{CA}+ ext{BI}\). One output of the sequence, SCG(13), is a subject of extensive research. It is known to surpass TREE(3), a number that arises from a related sequence.