OEIS sequence A272573 describes a sequence generated in the following way:
Start a spiral of numbers on a hexagonal tiling, with the initial hexagon as a(1) = 1. a(n) is the smallest positive integer not equal to or previously adjacent to its neighbors.
The sequence begins
I'm curious if there is some heuristic which explains why this gap appears. (In particular, the heuristic should also account for the fact that such a gap does not appear in A260643, the analogous sequence on a square grid.)