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

Terms

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