a(n) = Sum_{p|n, p prime} p^p.

Terms

a(0) =0a(1) =4a(2) =27a(3) =4a(4) =3125a(5) =31a(6) =823543a(7) =4a(8) =27a(9) =3129a(10) =285311670611a(11) =31a(13) =823547a(14) =3152a(15) =4a(17) =31a(19) =3129a(20) =823570a(21) =285311670615a(23) =31a(24) =3125