Row sum of triangle A279453.
Rotations and reflections of a placement are not counted. For numbers if they are to be counted, see A197458.
Table of n, a(n) for n=1..9.
Cf. A197458, A279453.
Sequence in context: A219692 A085078 A152543 * A306021 A122593 A267348
Adjacent sequences: A279451 A279452 A279453 * A279455 A279456 A279457
Heinrich Ludwig, Dec 24 2016