Left edge of the triangle in A033291.

Terms

a(0) =1a(1) =2a(2) =6a(3) =16a(4) =30a(5) =54a(6) =91a(7) =136a(8) =198a(9) =280a(10) =374a(11) =492a(12) =637a(13) =798a(14) =990a(15) =1216a(16) =1462a(17) =1746a(18) =2071a(19) =2420a(20) =2814a(21) =3256a(22) =3726a(23) =4248a(24) =4825a(25) =5434a(26) =6102a(27) =6832a(28) =7598a(29) =8430