Column l=3 of irregular triangle in A133709.

Terms

a(0) =0a(1) =3a(2) =35a(3) =131a(4) =347a(5) =767a(6) =1511a(7) =2744a(8) =4686a(9) =7623a(10) =11919a(11) =18029a(12) =26513a(13) =38051a(14) =53459a(15) =73706a(16) =99932a(17) =133467a(18) =175851a(19) =228855a(20) =294503a(21) =375095a(22) =473231a(23) =591836a(24) =734186a(25) =903935a(26) =1105143a(27) =1342305a(28) =1620381a(29) =1944827