Ceiling(4/3*Pi*n^3).

Terms

a(0) =0a(1) =5a(2) =34a(3) =114a(4) =269a(5) =524a(6) =905a(7) =1437a(8) =2145a(9) =3054a(10) =4189a(11) =5576a(12) =7239a(13) =9203a(14) =11495a(15) =14138a(16) =17158a(17) =20580a(18) =24430a(19) =28731a(20) =33511a(21) =38793a(22) =44603a(23) =50966a(24) =57906a(25) =65450a(26) =73623a(27) =82448a(28) =91953a(29) =102161