Numbers k for which sigma(k)/k - 1/5 is an integer.

Terms

a(0) =5a(1) =420a(2) =7440a(3) =8190a(4) =18600a(5) =121920a(6) =131040a(7) =95472000a(8) =102136320a(9) =197308800a(10) =433305600a(11) =503255040a(12) =71271827200a(13) =91967616000a(14) =128848035840a(15) =190066406400a(16) =287879454720a(17) =354560976000a(18) =799959888000