The following pictures show n unit circles covering the largest known circle (of radius r ).

n=1 r = 1 Trivial.

n=3 r = 2 / √3 = 1.154+ Trivial.

n=4 r = √2 = 1.414+ Trivial.

n=5 r = 1.641+ Proved by Károly Bezdek in 1983.

n=6 r = 1.798+ Proved by Károly Bezdek in 1979.

n=7 r = 2 Trivial.

n=8 r = 2.246+ Proved by Gábor Fejes Tóth in 1996.

n=9 r = √2 + 1 = 2.414+ Proved by Gábor Fejes Tóth in 1996.

n=10 r = 2.532+ Proved by Gábor Fejes Tóth in 2005.

n=11 r = 2.631+ Found by Hans Melissen in 1997.

n=12 r = 2.769+ Found by Hans Melissen in 1997.

n=13 r = 2.884+ Found by Jeremy Tan in 2018.

n=14 r = 3.014+ Found by Jeremy Tan in 2018.

n=15 r = 3.143+ Found by Jeremy Tan in 2018.

n=16 r = 3.244+ Found by Jeremy Tan in 2018.

n=17 r = 3.349+ Found by Jeremy Tan in 2018.

n=18 r = 3.446+ Found by Jeremy Tan in 2018.

n=19 r = √13 = 3.605+ Found by Jeremy Tan in 2018.

n=20 r = 3.692+ Found by Jeremy Tan in 2018.

n=21 r = 3.804+ Found by Jeremy Tan in 2018.

n=22 r = 3.948+ Found by Jeremy Tan in 2018.

n=23 r = 4.000+ Found by Jeremy Tan in 2018.

n=24 r = 4.076+ Found by Jeremy Tan in 2018.

n=25 r = √6 + √3 = 4.181+ Found by Jeremy Tan in 2018.