Numbers k such that sigma(k)^2 is divisible by k-1.

Terms

a(0) =2a(1) =3a(2) =5a(3) =10a(4) =33a(5) =55a(6) =82a(7) =129a(8) =136a(9) =145a(10) =261a(11) =351a(12) =385a(13) =406a(14) =442a(15) =513a(16) =649a(17) =897a(18) =1090a(19) =2241a(20) =4726a(21) =5185a(22) =8650a(23) =13601a(24) =17101a(25) =17641a(26) =18241a(27) =26625a(28) =26937a(29) =29697