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A228881
Minimum number of spheres touching a wall of the container in the densest packing of n equal spheres into a cube.
0
1, 2, 3, 4, 5, 6, 7, 8, 8, 9, 10, 10, 13, 14, 14, 13, 16, 17, 12, 14, 8, 12, 20, 15, 19, 20, 26, 22, 25, 26, 27, 28, 22
OFFSET
1,2
COMMENTS
Spheres that are not part of the rigid framework, "rattlers", are always assumed not to touch the walls of the container cube.
If optimal configurations can be obtained by taking away an arbitrary sphere from a configuration with a higher sphere count, a sphere touching the container wall is chosen.
LINKS
Hugo Pfoertner, Densest Packing of Spheres in a Cube (Java Visualization)
Eckard Specht, The best known packings of equal spheres in a cube, (complete up to N = 1000). [The title should be "The best packings known ..."! - N. J. A. Sloane, Mar 23 2021]
EXAMPLE
The first configuration in which there is an inner sphere not touching the walls occurs for n = 9, with 8 spheres in the corners of the cube and one sphere in the center of the cube. Therefore a(9) = 8.
CROSSREFS
Cf. A084824.
Sequence in context: A079631 A347623 A269849 * A252373 A245338 A160755
KEYWORD
nonn,more,changed
AUTHOR
Hugo Pfoertner, Sep 13 2013
EXTENSIONS
a(25)-a(33) from Hugo Pfoertner, Mar 23 2021
STATUS
approved