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

Terms

a(0) =2a(1) =5a(2) =11a(3) =16a(4) =27a(5) =34a(6) =48a(7) =60a(8) =77a(9) =88a(10) =115a(11) =128a(12) =151a(13) =174a(14) =204a(15) =221a(16) =259a(17) =278a(18) =319a(19) =350a(20) =385a(21) =408a(22) =467a(23) =497a(24) =538a(25) =577a(26) =632a(27) =661a(28) =732a(29) =763