The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A182947 Number of complete sphere stacks on a triangular base with side length n. 1
 1, 1, 2, 9, 76, 1134, 33464, 1951187 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Start with a layer of spheres closely packed in an equilateral triangle 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 Table of n, a(n) for n=1..8. EXAMPLE For n=3 there are two complete stacks, so a(3)=2. . 3 layers, 10 spheres 2 layers, 7 spheres . 1 1 / \ / \ / 2 \ / \ 1-----1 1-----1 / \ 3 / \ / \ 2 / \ / 2 \ / 2 \ / \ / \ 1-----1-----1 1-----1-----1 CROSSREFS Cf. A182948 = spheres on a rhombic base. Sequence in context: A058164 A006059 A277406 * A006041 A192551 A121131 Adjacent sequences: A182944 A182945 A182946 * A182948 A182949 A182950 KEYWORD nonn,more AUTHOR David Scambler, Dec 14 2010 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified February 24 10:53 EST 2024. Contains 370295 sequences. (Running on oeis4.)