Primes of the form sigma_4(k)/sigma_2(k), arising in A066109.

Terms

a(0) =13a(1) =73a(2) =313a(3) =601a(4) =28393a(5) =83233a(6) =922561a(7) =3416953a(8) =13842121a(9) =47451433a(10) =141146281a(11) =212601841a(12) =234750601a(13) =294482761a(14) =2750006041a(15) =3262751521a(16) =4362404353a(17) =4784281393a(18) =5236041961a(19) =9354855121a(20) =9597826993a(21) =13564461457a(22) =16936647121