Integer reached in A072340.

Terms

a(0) =1a(1) =8a(3) =2a(4) =7a(5) =8a(6) =3a(8) =220a(9) =4a(10) =227370a(11) =560a(12) =5a(13) =32a(14) =34a(15) =6a(16) =1995a(18) =7a(19) =11983136a(21) =8a(22) =75a(23) =78a(24) =9