Numbers k for which exactly 4 applications of A000005 are needed to reach 2.

Terms

a(0) =12a(1) =18a(2) =20a(3) =24a(4) =28a(5) =30a(6) =32a(7) =40a(8) =42a(9) =44a(10) =45a(11) =48a(12) =50a(13) =52a(14) =54a(15) =56a(16) =63a(17) =66a(18) =68a(19) =70a(20) =75a(21) =76a(22) =78a(23) =80a(24) =88a(25) =92a(26) =98a(27) =99a(28) =102a(29) =104