a(n) = Sum_{k=1..n} floor(n/k)^3.

Terms

a(0) =1a(1) =9a(2) =29a(3) =74a(4) =136a(5) =254a(6) =382a(7) =596a(8) =833a(9) =1173a(10) =1505a(11) =2057a(12) =2527a(13) =3209a(14) =3921a(15) =4856a(16) =5674a(17) =6928a(18) =7956a(19) =9474a(20) =10882a(21) =12608a(22) =14128a(23) =16506a(24) =18369a(25) =20797a(26) =23141a(27) =26129a(28) =28567a(29) =32259