The first requirement is 1*3 matching, the second requirement is (1+2)*3 matching, the third requirement is (1+2+3)*3 matching, and the fourth requirement is (1+2+3+4) *. ...
( 1+2+3+4+……+n)*3
=(n*(n- 1))*3/2
The nth graph needs (n*(n- 1))*3/2.
(A match) has n 2 triangles.