Number of triangular regions in regular n-gon with all diagonals drawn.

Terms

a(0) =1a(1) =4a(2) =10a(3) =18a(4) =35a(5) =56a(6) =90a(7) =120a(8) =176a(9) =276a(10) =377a(11) =476a(12) =585a(13) =848a(14) =1054a(15) =1404a(16) =1653a(17) =2200a(18) =2268a(19) =2992a(20) =3749a(21) =4416a(22) =5000a(23) =6292a(24) =6777a(25) =8316a(26) =9222a(27) =11670a(28) =11501a(29) =14368