a(n) = Sum_{k=1..n} k * tau_3(k), where tau_3 is A007425.

Terms

a(0) =1a(1) =7a(2) =16a(3) =40a(4) =55a(5) =109a(6) =130a(7) =210a(8) =264a(9) =354a(10) =387a(11) =603a(12) =642a(13) =768a(14) =903a(15) =1143a(16) =1194a(17) =1518a(18) =1575a(19) =1935a(20) =2124a(21) =2322a(22) =2391a(23) =3111a(24) =3261a(25) =3495a(26) =3765a(27) =4269a(28) =4356a(29) =5166