Table of n, a(n) for n=2..10.
The 8 points of the 2 X 2 X 2 grid define 20 planes: the 6 faces of the cube, 6 planes formed by an edge and its opposite edge, and 8 planes defined by the three vertices surrounding a given vertex. So, a(2)=20.
Cf. A222267, A270579.
Sequence in context: A000827 A241261 A118552 * A255492 A092087 A008270
Adjacent sequences: A270575 A270576 A270577 * A270579 A270580 A270581
Clive Tooth, Mar 19 2016