Numbers k such that sigma(x) = k has exactly 4 solutions.

Terms

a(0) =96a(1) =120a(2) =180a(3) =312a(4) =372a(5) =420a(6) =434a(7) =456a(8) =540a(9) =546a(10) =560a(11) =624a(12) =702a(13) =728a(14) =798a(15) =816a(16) =930a(17) =1064a(18) =1120a(19) =1170a(20) =1404a(21) =1632a(22) =1638a(23) =1674a(24) =1710a(25) =1776a(26) =1792a(27) =1944a(28) =2100a(29) =2240