Number of four-prime Carmichael numbers less than 10^n.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =4a(6) =19a(7) =55a(8) =144a(9) =314a(10) =619a(11) =1179a(12) =2102a(13) =3639a(14) =6042a(15) =9938a(16) =16202a(17) =25758a(18) =40685a(19) =63343a(20) =98253a(21) =151566a(22) =232742a(23) =357078a(24) =548265