a(n) = Sum_{d|n} d * sigma(n/d, d).

Terms

a(0) =1a(1) =5a(2) =7a(3) =21a(4) =11a(5) =65a(6) =15a(7) =133a(8) =106a(9) =245a(10) =23a(11) =1077a(12) =27a(13) =1041a(14) =1637a(15) =3365a(16) =35a(17) =9992a(18) =39a(19) =18361a(20) =16401a(21) =22841a(22) =47a(23) =134461a(24) =15686a(25) =106917a(26) =179494a(27) =355173a(28) =59a(29) =1220075