Numbers k such that sigma(x) = k has a unique solution.

Terms

a(0) =1a(1) =3a(2) =4a(3) =6a(4) =7a(5) =8a(6) =13a(7) =14a(8) =15a(9) =20a(10) =28a(11) =30a(12) =36a(13) =38a(14) =39a(15) =40a(16) =44a(17) =57a(18) =62a(19) =63a(20) =68a(21) =74a(22) =78a(23) =91a(24) =93a(25) =102a(26) =110a(27) =112a(28) =121a(29) =127