Squared radii of the circles around (0,0) that contain record numbers of lattice points.

Terms

a(0) =0a(1) =1a(2) =5a(3) =25a(4) =65a(5) =325a(6) =1105a(7) =4225a(8) =5525a(9) =27625a(10) =71825a(11) =138125a(12) =160225a(13) =801125a(14) =2082925a(15) =4005625a(16) =5928325a(17) =29641625a(18) =77068225a(19) =148208125a(20) =243061325a(21) =1215306625a(22) =3159797225a(23) =6076533125a(24) =12882250225a(25) =53716552825a(26) =64411251125