Tribonacci left-bounded rhombic triangle.

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =2a(5) =1a(6) =7a(7) =7a(8) =3a(9) =1a(10) =18a(11) =20a(12) =12a(13) =4a(14) =1a(15) =48a(16) =59a(17) =40a(18) =18a(19) =5a(20) =1a(21) =132a(22) =174a(23) =132a(24) =68a(25) =25a(26) =6a(27) =1a(28) =372a(29) =517