Right edge of triangular table A138612.

Terms

a(0) =1a(1) =4a(2) =12a(3) =28a(4) =53a(5) =91a(6) =141a(7) =207a(8) =297a(9) =401a(10) =534a(11) =683a(12) =869a(13) =1081a(14) =1327a(15) =1601a(16) =1912a(17) =2275a(18) =2665a(19) =3095a(20) =3569a(21) =4110a(22) =4682a(23) =5314a(24) =5996a(25) =6744a(26) =7535a(27) =8394a(28) =9320a(29) =10303