Numbers n such that sigma(phi(n)) = n.

Terms

a(0) =1a(1) =3a(2) =15a(3) =28a(4) =255a(5) =744a(6) =2418a(7) =20440a(8) =65535a(9) =548856a(10) =2835756a(11) =4059264a(12) =4451832a(13) =10890040a(14) =13192608a(15) =23001132a(16) =54949482a(17) =110771178a(18) =220174080a(19) =445701354a(20) =4294967295a(21) =16331433888a(22) =18377794080a(23) =94951936080a(24) =204721968000a(25) =386940247200a(26) =601662398400