a(n) is the smallest number whose digits are 1's and 0's that cannot be written as a concatenation of any of the previous terms (not repeating any terms in the concatenation). a(0) = 0.

A309870

a(n) is the smallest number whose digits are 1's and 0's that cannot be written as a concatenation of any of the previous terms (not repeating any terms in the concatenation). a(0) = 0.