Numbers k such that sigma(phi(k)) == 0 (mod k).

Terms

a(0) =1a(1) =3a(2) =15a(3) =28a(4) =255a(5) =744a(6) =1209a(7) =2418a(8) =20440a(9) =65535a(10) =548856a(11) =2835756a(12) =4059264a(13) =4451832a(14) =10890040a(15) =13192608a(16) =23001132a(17) =23746333a(18) =27474741a(19) =54949482a(20) =55385589a(21) =110771178a(22) =220174080a(23) =222850677a(24) =445701354a(25) =4294967295a(26) =16331433888a(27) =18377794080a(28) =94951936080