For any n > 0, let S_n(0) be the concatenation of the numbers in the range 1..n (in increasing order); for k=1..n, S_n(k) is obtained by removing the rightmost occurrence of k in S_n(k-1), if any; a(n) is the numerical value of S_n(n) (or 0 if S_n(n) is empty).

A330398

For any n > 0, let S_n(0) be the concatenation of the numbers in the range 1..n (in increasing order); for k=1..n, S_n(k) is obtained by removing the rightmost occurrence of k in S_n(k-1), if any; a(n) is the numerical value of S_n(n) (or 0 if S_n(n) is empty).