Squarefree composite numbers n such that n*sigma(n) is of the form k*(k+1).

Terms

a(0) =6a(1) =42a(2) =1430a(3) =3686a(4) =5685a(5) =23815a(6) =60235a(7) =129778a(8) =370991a(9) =652289a(10) =654545a(11) =660265a(12) =795405a(13) =801645a(14) =1532170a(15) =3413267a(16) =3457597a(17) =4235270a(18) =4282330a(19) =8107937a(20) =9679187a(21) =10835013a(22) =15464685a(23) =15963578a(24) =16636503a(25) =24976497a(26) =28122458a(27) =29595310a(28) =34759879a(29) =35642479