A071159 Integers whose decimal expansion start with 1, do not contain zeros and each successive digit to the right is at most one greater than the previous.

1, 11, 12, 111, 112, 121, 122, 123, 1111, 1112, 1121, 1122, 1123, 1211, 1212, 1221, 1222, 1223, 1231, 1232, 1233, 1234, 11111, 11112, 11121, 11122, 11123, 11211, 11212, 11221, 11222, 11223, 11231, 11232, 11233, 11234, 12111, 12112, 12121