a(n) = sigma_3(n) - sigma_2(n).

Terms

a(0) =0a(1) =4a(2) =18a(3) =52a(4) =100a(5) =202a(6) =294a(7) =500a(8) =666a(9) =1004a(10) =1210a(11) =1834a(12) =2028a(13) =2846a(14) =3268a(15) =4340a(16) =4624a(17) =6358a(18) =6498a(19) =8652a(20) =9132a(21) =11378a(22) =11638a(23) =15530a(24) =15100a(25) =18932a(26) =19620a(27) =24062a(28) =23548a(29) =30452