The community supporting the On-Line Encyclopedia of Integer Sequences (OEIS) recently had nominations to determine which sequence should be given the designation A400000. The winning sequence is shown by the illustration above and is called the City-Building Sequence. The city-building sequence is the integer sequence obtained by placing buildings at consecutive integer positions along a straight street, choosing each height to be the smallest nonnegative integer equal to the number of earlier rooftops visible from its top. A rooftop is visible when every intervening rooftop lies on or below the line segment joining it to the new rooftop. In particular, collinear rooftops count separately. It could also be called a rooftop visibility sequence. The first building has height 0, and the first terms are 0, 1, 1, 2, 1, 2, 1, 3, 1, 2, 1, 3, 1, 2, 1, 10, ... (OEIS A400000).
There were many sequences nominated to have the honor of being A400000 and the many of these were awarded designations near A400000: https://oeis.org/wiki/A400K_Winners.
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