a(n) = Sum_{k=1..n} floor(n^2/k).

Terms

a(0) =0a(1) =1a(2) =6a(3) =16a(4) =33a(5) =56a(6) =88a(7) =125a(8) =172a(9) =227a(10) =291a(11) =363a(12) =445a(13) =533a(14) =633a(15) =743a(16) =861a(17) =989a(18) =1128a(19) =1275a(20) =1434a(21) =1601a(22) =1779a(23) =1967a(24) =2170a(25) =2376a(26) =2597a(27) =2827a(28) =3072a(29) =3324