In a 6 by 6 grid, how many pathways can be drawn from S to F, S is the top left corner and F is the bottom right corner (always moving to the right or down) that cross the main diagonal at least once? (You can use the Catalan sequence for this question, but it is possible to solve without it.) Don't try drawing all the pathways!

(A) 520

(B) 610

(C) 630

(D) 660

(E) 720

jonathanxu999 Jan 21, 2018