Number of solutions to x^2 + y^2 + z^2 < n^2; number of lattice points inside a sphere of radius n.

Terms

a(0) =0a(1) =1a(2) =27a(3) =93a(4) =251a(5) =485a(6) =895a(7) =1365a(8) =2103a(9) =2969a(10) =4139a(11) =5497a(12) =7123a(13) =9093a(14) =11459a(15) =13997a(16) =17071a(17) =20377a(18) =24303a(19) =28545a(20) =33371a(21) =38641a(22) =44395a(23) =50733a(24) =57747a(25) =65117a(26) =73447a(27) =82201a(28) =91911a(29) =101769