User:Kprateek88/HigmanProof

Formal statement
Let $$(\Sigma, \leq)$$ be a well-quasi-order. Extend $$\leq$$ to a relation on $$\Sigma^*$$ as follows: $$a_1 \ldots a_k \leq b_1 \ldots b_n$$ if there exist integers $$1 \leq n_1 < \ldots < n_k \leq n$$ such that for all $$i$$, $$a_i \leq b_{n_i}$$.