

A182948


Number of complete sphere stacks on a rhombic base with side lengths n.


1




OFFSET

1,2


COMMENTS

Start with a layer of spheres closely packed in a rhombus (diamond) of side n >= 1. Add spheres by resting them in any of the hollows between three touching spheres in the layer below. Continue until no more sites are available. a(n) is the number of distinct complete stacks that can be built.


LINKS



EXAMPLE

For n=2 there are two complete stacks so a(2)=2.
.
11 11
\ / \ \ / \
\ 2 / \ \ / \
\ / \ or \ / \
\ / \ \ / 2 \
\ / \ \ / \
11 11


CROSSREFS

Cf. A182947 = spheres on a triangular base.


KEYWORD

nonn,more


AUTHOR



STATUS

approved



