| 3. |  |
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A = 1/2 = .5 Trivial. One of an infinite family of solutions. Symmetric about a diagonal. |
| 4. |  |
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A = 1/2 = .5 Trivial. Completely symmetric. |
| 5. |  |
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A = √3 / 9 = .19245+ Proved optimal by Yang Lu, Zhang Jingzhong, and Zeng Zhenbing in 1991. Symmetric about a diagonal. |
| 6. |  |
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A = 1/8 = .125 Proved optimal by A. Dress, L. Yang, and Z. B. Zeng in 1995. One of an infinite family of solutions. Vertically and horizontally symmetric. |
| 7. |  |
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A = .08386+ Found by F. Comellas and J. Yebra, December 2001. Proved optimal by Zhenbing Chen and Liangyu Chen in 2011. Not symmetric. |
| 8. |  |
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A = (√13–1) / 36 = .07237+ Found by F. Comellas and J. Yebra, December 2001. Proved optimal by L. Dehbi and Z. Zeng in 2022. 180o Rotationally symmetric. |
| 9. |  |
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A = (9√65–55) / 320 = .05487+ Found by F. Comellas and J. Yebra, December 2001. Proved optimal by Nathan Sudermann-Merx in March 2026. Symmetric about a diagonal. |
| 10. |  |
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A = .04654+ Found by F. Comellas and J. Yebra in December 2001. Symmetric about both diagonals. |
| 11. |  |
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A = 1/27 = .03704+ Found by Michael Goldberg in 1972. Horizontally symmetric. |
| 12. |  |
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A = .03260+ Found by F. Comellas and J. Yebra in December 2001. Completely symmetric. |
| 13. |  |
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A = .02702+ Found by Peter Karpov in August 2011. Not symmetric. |
| 14. |  |
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A = .02430+ Found by Mark Beyleveld in August 2006. Vertically and horizontally symmetric. |
| 15. |  |
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A = .02111+ Found by Peter Karpov in August 2011. Not symmetric. |
| 16. |  |
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A = 7 / 341 = .02053+ Found by Mark Beyleveld in August 2006. 180o Rotationally symmetric. |
| 17. |  |
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 |
 |
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A = .016481+ Found by Tej Stead in July 2026. Not symmetric. |
| 18. |  |
A = .01447+ Found by William Shanley in July 2026. Vertically and horizontally symmetric. |
| 19. |  |
A = 0.01338+ Found by William Shanley in July 2026. Not symmetric. |
| 20. |  |
A = 0.01291+ Found by William Shanley in July 2026. 180o Rotationally symmetric. |
| 21. |  |
 |
 |
 |
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A = .00987+ Found by Tej Stead in July 2026. Not symmetric. |
| 22. |  |
 |
 |
 |
 |
 |
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A = .00886+ Found by Tej Stead in July 2026. Not symmetric. |
| 23. |  |
 |
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A = .00770+ Found by Tej Stead in July 2026. Not symmetric. |
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 |
 |
| 24. |  |
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A = .00692+ Found by Tej Stead in July 2026. Not symmetric. |
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 |
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| 25. |  |
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 |
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A = .00669+ Found by Tej Stead in July 2026. Not symmetric. |
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| 26. |  |
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A = .00603+ Found by Tej Stead in July 2026. Not symmetric. |
| 27. |  |
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 |
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A = .00542+ Found by Tej Stead in July 2026. Not symmetric. |
| 28. |  |
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 |
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A = .00501+ Found by Tej Stead in July 2026. Not symmetric. |
More information is available at Mathworld.