Why is it that the inequality:
$R(r, b)\leq R(r-1,b)+R(r,b-1)$ holds $\forall r,b \in \mathbb{N}$
Is there some form of conventional proof? Lecturer sent me some notes to have a look at with regards to Ramsey Numbers/Theory, if not a direct proof posted below some links would be helpful if possible.
Cheers