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

Terms

a(0) =1a(1) =6a(2) =14a(3) =31a(4) =47a(5) =81a(6) =103a(7) =153a(8) =195a(9) =260a(10) =299a(11) =401a(12) =453a(13) =542a(14) =643a(15) =761a(16) =834a(17) =999a(18) =1078a(19) =1266a(20) =1397a(21) =1548a(22) =1650a(23) =1932a(24) =2068a(25) =2257a(26) =2444a(27) =2707a(28) =2831a(29) =3203