A031098 Write n in base 9, then complement each digit (d -> 4-d) and juxtapose.

7, 6, 5, 4, 3, 2, 1, 0, 7, 8, 7, 7, 7, 6, 7, 5, 7, 4, 7, 3, 7, 2, 7, 1, 7, 0, 6, 8, 6, 7, 6, 6, 6, 5, 6, 4, 6, 3, 6, 2, 6, 1, 6, 0, 5, 8, 5, 7, 5, 6, 5, 5, 5, 4, 5, 3, 5, 2, 5, 1, 5, 0, 4, 8, 4, 7, 4, 6, 4, 5, 4, 4, 4, 3, 4, 2, 4, 1, 4, 0, 3, 8, 3, 7, 3, 6, 3, 5, 3, 4