Numbers k such that the denominator of sigma(sigma(k))/k is equal to 2.

Terms

a(0) =30a(1) =2046a(2) =245760a(3) =301056a(4) =450560a(5) =1171456a(6) =1351680a(7) =3514368a(8) =14515200a(9) =16760832a(10) =19611648a(11) =77220864a(12) =159373824a(13) =357291648a(14) =391444480a(15) =477216768a(16) =555714432a(17) =754928640a(18) =765414240a(19) =1006602240a(20) =1761500160a(21) =2330913312a(22) =4314834944a(23) =8369053056a(24) =20449394784a(25) =37949317120