a(n) = Sum_{k=1..n} k^2*sigma_2(k), where sigma_2 is A001157.

Terms

a(0) =1a(1) =21a(2) =111a(3) =447a(4) =1097a(5) =2897a(6) =5347a(7) =10787a(8) =18158a(9) =31158a(10) =45920a(11) =76160a(12) =104890a(13) =153890a(14) =212390a(15) =299686a(16) =383496a(17) =530916a(18) =661598a(19) =879998a(20) =1100498a(21) =1395738a(22) =1676108a(23) =2165708a(24) =2572583a(25) =3147183a(26) =3744963a(27) =4568163a(28) =5276285a(29) =6446285