The unique number 1 of 1 digit can be read in 1 number of 2 digits = 10, hence c(n) = 1.
The 2 numbers of 2 digits 10 and 11 can be read in 1 number of 3 digits = 110, hence c(2)=1.
The four numbers of 3 digits 100,101,110,111 need 3 digits of 4 digits : e.g 1000 (100)1010(101)1110 (110 and 111); 2 numbers are not enough because 1010 for example contains only one number of 3 digits and for the second reason that 1100 and 1101 contain each the number 110.
