Maximal multiplicative persistence (or length) of any n-digit number.

Terms

a(0) =1a(1) =4a(2) =5a(3) =6a(4) =7a(5) =7a(6) =8a(7) =9a(8) =9a(9) =10a(10) =10a(11) =10a(12) =10a(13) =10a(14) =11a(15) =11a(16) =11a(17) =11a(18) =11a(19) =11a(20) =11a(21) =11a(22) =11a(23) =11a(24) =11a(25) =11a(26) =11a(27) =11a(28) =11a(29) =11