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..8.
Cf. A112389, A123762 - A123827, A123829 - A123849.
Sequence in context: A116508 A055659 A218368 * A273921 A182607 A218284
Adjacent sequences: A123813 A123814 A123815 * A123817 A123818 A123819
Søren Eilers, Oct 29 2006