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

Terms

a(0) =0a(1) =1a(2) =4a(3) =13a(4) =22a(5) =50a(6) =68a(7) =116a(8) =162a(9) =236a(10) =278a(11) =437a(12) =498a(13) =634a(14) =794a(15) =1018a(16) =1118a(17) =1450a(18) =1574a(19) =1975a(20) =2276a(21) =2598a(22) =2774a(23) =3519a(24) =3834a(25) =4273a(26) =4746a(27) =5490a(28) =5772a(29) =6887