Numbers k such that sigma(x) = k has exactly 2 solutions.

Terms

a(0) =12a(1) =18a(2) =31a(3) =32a(4) =54a(5) =56a(6) =80a(7) =98a(8) =104a(9) =108a(10) =114a(11) =124a(12) =126a(13) =128a(14) =132a(15) =140a(16) =152a(17) =156a(18) =182a(19) =186a(20) =210a(21) =264a(22) =272a(23) =280a(24) =308a(25) =320a(26) =342a(27) =378a(28) =390a(29) =392