a(n) = Sum_{k=1..n} k^2*tau(k), where tau is A000005.

Terms

a(0) =1a(1) =9a(2) =27a(3) =75a(4) =125a(5) =269a(6) =367a(7) =623a(8) =866a(9) =1266a(10) =1508a(11) =2372a(12) =2710a(13) =3494a(14) =4394a(15) =5674a(16) =6252a(17) =8196a(18) =8918a(19) =11318a(20) =13082a(21) =15018a(22) =16076a(23) =20684a(24) =22559a(25) =25263a(26) =28179a(27) =32883a(28) =34565a(29) =41765