Numbers k such that sigma(k+1) divides sigma(k-1).

Terms

a(0) =34a(1) =55a(2) =285a(3) =367a(4) =835a(5) =849a(6) =919a(7) =1241a(8) =1505a(9) =2911a(10) =2914a(11) =3305a(12) =4149a(13) =4188a(14) =6111a(15) =6903a(16) =7170a(17) =7913a(18) =8506a(19) =9360a(20) =10251a(21) =10541a(22) =12566a(23) =15086a(24) =17273a(25) =17815a(26) =19005a(27) =19689a(28) =21411a(29) =21462