a(n) = Product_{d|n} sigma(d) where sigma = A000203.

Terms

a(0) =1a(1) =3a(2) =4a(3) =21a(4) =6a(5) =144a(6) =8a(7) =315a(8) =52a(9) =324a(10) =12a(11) =28224a(12) =14a(13) =576a(14) =576a(15) =9765a(16) =18a(17) =73008a(18) =20a(19) =95256a(20) =1024a(21) =1296a(22) =24a(23) =25401600a(24) =186a(25) =1764a(26) =2080a(27) =225792a(28) =30a(29) =26873856