Numbers k such that sigma_2(k) = sigma_2(phi(k)).

Terms

a(0) =1a(1) =7a(2) =11891a(3) =130801a(4) =273493a(5) =1438811a(6) =3008423a(7) =6290339a(8) =15826921a(9) =33092653a(10) =69193729a(11) =144677797a(12) =174096131a(13) =364019183a(14) =761131019a(15) =1591455767a(16) =1915057441a(17) =3327589331a(18) =4004211013a(19) =8372441209a(20) =17506013437a(21) =21065631851a(22) =36603482641a(23) =44046321143a(24) =76534554613a(25) =92096853299