A sticky polyhex is defined as follows:
- A single dihex (polyhex of size 2) is a sticky polyhex.
- If a polyhex X is sticky, X plus a dihex Y is also sticky if X and Y share at least two unit sides.
- Any polyhex that cannot be formed by the above definition is not sticky.
This sequence counts free polyhexes; two polyhexes which are equivalent under reflection and/or rotation are counted only once.
a(n) < A000228(2n) for n > 1.