Numbers k for which gcd(2k, sigma(k)) = 2k.

Terms

a(0) =6a(1) =28a(2) =496a(3) =8128a(4) =30240a(5) =32760a(6) =2178540a(7) =23569920a(8) =33550336a(9) =45532800a(10) =142990848a(11) =1379454720a(12) =8589869056a(13) =43861478400a(14) =66433720320a(15) =137438691328a(16) =153003540480a(17) =403031236608a(18) =704575228896