a(n) = Sum_{k=1..n} sigma_3(k) * floor(n/k).

Terms

a(0) =1a(1) =11a(2) =40a(3) =123a(4) =250a(5) =540a(6) =885a(7) =1553a(8) =2339a(9) =3609a(10) =4942a(11) =7349a(12) =9548a(13) =12998a(14) =16681a(15) =22030a(16) =26945a(17) =34805a(18) =41666a(19) =52207a(20) =62212a(21) =75542a(22) =87711a(23) =107083a(24) =122961a(25) =144951a(26) =166177a(27) =194812a(28) =219203a(29) =256033