Numbers k such that sigma(sigma(sigma(k))) == 6*sigma(k).

Terms

a(0) =20a(1) =26a(2) =41a(3) =44a(4) =65a(5) =83a(6) =132a(7) =133a(8) =140a(9) =182a(10) =188a(11) =195a(12) =249a(13) =287a(14) =299a(15) =420a(16) =546a(17) =564a(18) =620a(19) =644a(20) =764a(21) =806a(22) =861a(23) =897a(24) =1001a(25) =1115a(26) =1169a(27) =1271a(28) =28644a(29) =32172