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

Terms

a(0) =1a(1) =9a(2) =31a(3) =75a(4) =146a(5) =256a(6) =406a(7) =610a(8) =870a(9) =1194a(10) =1590a(11) =2069a(12) =2631a(13) =3286a(14) =4043a(15) =4910a(16) =5889a(17) =6997a(18) =8228a(19) =9600a(20) =11114a(21) =12781a(22) =14605a(23) =16599a(24) =18760a(25) =21106a(26) =23636a(27) =26363a(28) =29292a(29) =32429