The base block is not counted among the n and must be the only block in the bottom layer of the building.
Table of n, a(n) for n=1..9.
Cf. A112389, A123762 - A123827, A123829 - A123849.
Sequence in context: A335508 A176735 A286786 * A022520 A020236 A068624
Adjacent sequences: A123789 A123790 A123791 * A123793 A123794 A123795
Søren Eilers, Oct 29 2006