a(n)=number of Gaussian integers z=a+bi satisfying n-1<|z|<=n, a>=0, 0<=b<a.

Terms

a(0) =0a(1) =1a(2) =1a(3) =2a(4) =3a(5) =4a(6) =4a(7) =5a(8) =6a(9) =7a(10) =8a(11) =8a(12) =8a(13) =11a(14) =11a(15) =12a(16) =11a(17) =13a(18) =14a(19) =15a(20) =16a(21) =15a(22) =18a(23) =17a(24) =18a(25) =21a(26) =20a(27) =21a(28) =21a(29) =22