let catalan n = 
	let t = Array.make (n+1) 0 in
	t.(0) <- 1;
	for i=1 to n do
		for k=0 to i-1 do
			t.(i) <- (t.(k)*t.(i-1-k)) + t.(i)
		done
	done;
	t.(n);;

catalan 5;;

let rec est_triee l = match l with
	| [] -> true
	| [a] -> true
	| a::(b::t) -> a<=b && est_triee b::t;;