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

Terms

a(0) =1a(1) =5a(2) =11a(3) =22a(4) =33a(5) =52a(6) =67a(7) =93a(8) =117a(9) =149a(10) =174a(11) =219a(12) =250a(13) =293a(14) =339a(15) =392a(16) =434a(17) =500a(18) =546a(19) =619a(20) =680a(21) =748a(22) =804a(23) =903a(24) =969a(25) =1051a(26) =1131a(27) =1230a(28) =1301a(29) =1422