Number of integer points (x,y,z) at distance <= 0.5 from sphere of radius n.

Terms

a(0) =1a(1) =18a(2) =62a(3) =98a(4) =210a(5) =350a(6) =450a(7) =602a(8) =762a(9) =1142a(10) =1250a(11) =1458a(12) =1814a(13) =2178a(14) =2498a(15) =2622a(16) =3338a(17) =3722a(18) =4170a(19) =4358a(20) =5034a(21) =5714a(22) =5982a(23) =6602a(24) =7130a(25) =8034a(26) =8606a(27) =9066a(28) =9962a(29) =10550