Circle packing in a circle is a two-dimensional packing problem with the objective of packing unit circles into the smallest possible larger circle.
If more than one optimal solution exists, all are shown. [1]
Enclosing circle radius | Density | Optimality | Layout(s) of the circles | |
---|---|---|---|---|
1 | 1 | 1.0 | Trivially optimal. | |
2 | 2 | 0.5 | Trivially optimal. | |
3 | 2.155... | 0.6466... | Trivially optimal. | |
4 | 2.414... | 0.6864... | Trivially optimal. | |
5 | 2.701... | 0.6854... | Proved optimal by Graham (1968) [2] | |
6 | 3 | 0.6666... | Proved optimal by Graham (1968) [2] | |
7 | 3 | 0.7777... | Trivially optimal. | |
8 | 3.304... | 0.7328... | Proved optimal by Pirl (1969) [3] | |
9 | 3.613... | 0.6895... | Proved optimal by Pirl (1969) [3] | |
10 | 3.813... | 0.6878... | Proved optimal by Pirl (1969) [3] | |
11 | 3.923... | 0.7148... | Proved optimal by Melissen (1994) [4] | |
12 | 4.029... | 0.7392... | Proved optimal by Fodor (2000) [5] | |
13 | 4.236... | 0.7245... | Proved optimal by Fodor (2003) [6] | |
14 | 4.328... | 0.7474... | Proved optimal by Ekanayake and LaFountain (2024). [7] | |
15 | 4.521... | 0.7339... | Conjectured optimal by Pirl (1969). [8] | |
16 | 4.615... | 0.7512... | Conjectured optimal by Goldberg (1971). [8] | |
17 | 4.792... | 0.7403... | Conjectured optimal by Reis (1975). [8] | |
18 | 4.863... | 0.7609... | Conjectured optimal by Pirl (1969), with additional arrangements by Graham, Lubachevsky, Nurmela, and Östergård (1998). [8] | |
19 | 4.863... | 0.8032... | Proved optimal by Fodor (1999) [9] | |
20 | 5.122... | 0.7623... | Conjectured optimal by Goldberg (1971). [8] |
Only 26 optimal packings are thought to be rigid (with no circles able to "rattle"). Numbers in bold are prime:
Of these, solutions for n = 2, 3, 4, 7, 19, and 37 achieve a packing density greater than any smaller number > 1. (Higher density records all have rattles.) [10]
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