a(n) = Sum_{k=1..n} floor((n/k) * floor((n/k) * floor(n/k))).

Terms

a(0) =1a(1) =9a(2) =29a(3) =74a(4) =140a(5) =254a(6) =391a(7) =601a(8) =851a(9) =1183a(10) =1546a(11) =2058a(12) =2580a(13) =3244a(14) =3986a(15) =4876a(16) =5795a(17) =6959a(18) =8105a(19) =9540a(20) =11012a(21) =12692a(22) =14391a(23) =16546a(24) =18590a(25) =20966a(26) =23425a(27) =26255a(28) =28992a(29) =32344