Ramsey number $R(n,n) > (n-1)^2$

772 Views Asked by At

I got an home work assignment, prove that:

$R(n,n) > (n-1)^2$

Note that I saw on Wikipedia that for subgraph of $K_n$ with k vertices, $R(k,k) > 2^{k/2}$.

I tried to work with that, but still it doesn't really helps me.

1

There are 1 best solutions below

3
On BEST ANSWER

The union of $n-1$ copies of $K_{n-1}$ is a graph with $(n-1)^2$ vertices which doesn't contain $K_n$ nor $n$ independent vertices. This proves $R(n,n) > (n-1)^2$ by definition of the Ramsey number.