Numbers k such that sigma(k) == 4 (mod k).

Terms

a(0) =1a(1) =3a(2) =9a(3) =12a(4) =70a(5) =88a(6) =1888a(7) =4030a(8) =5830a(9) =32128a(10) =521728a(11) =1848964a(12) =8378368a(13) =34359083008a(14) =66072609790a(15) =549753192448