A031251 Write n in base 5, then complement each digit (d -> 4-d) and juxtapose.

3, 2, 1, 0, 3, 4, 3, 3, 3, 2, 3, 1, 3, 0, 2, 4, 2, 3, 2, 2, 2, 1, 2, 0, 1, 4, 1, 3, 1, 2, 1, 1, 1, 0, 0, 4, 0, 3, 0, 2, 0, 1, 0, 0, 3, 4, 4, 3, 4, 3, 3, 4, 2, 3, 4, 1, 3, 4, 0, 3, 3, 4, 3, 3, 3, 3, 3, 2, 3, 3, 1, 3, 3, 0, 3, 2, 4, 3, 2, 3, 3, 2, 2, 3, 2, 1, 3, 2, 0, 3