Concatenate the ternary strings for 1,2,...,n-1, n, n-1, ..., 2,1.

A360504

Concatenate the ternary strings for 1,2,...,n-1, n, n-1, ..., 2,1.

Terms

    a(0) =1a(1) =121a(2) =121021a(3) =1210111021

External references