A333572 a(n) is the number of Gaussian integers z with 0 < |z| <= n/2.

0, 4, 8, 12, 20, 28, 36, 48, 68, 80, 96, 112, 136, 148, 176, 196, 224, 252, 292, 316, 348, 376, 420, 440, 488, 528, 576, 612, 664, 708, 748, 796, 860, 900, 972, 1008, 1084, 1128, 1200, 1256, 1312, 1372, 1456, 1516, 1596, 1652, 1740, 1792, 1884, 1960, 2052, 2120

Offset: 1

Author

Hugo Pfoertner, Mar 27 2020

Keywords

• nonn

Links

• Robert Israel, Table of n, a(n) for n = 1..2000

Crossrefs

Cf. A004018, A232705, A333462, A333573.

Programs

Maple

N:= 100: # for a(1)..a(N)
V:= Vector(N):
for x from 1 to N/2 do
  for y from 0 to x do
    v:= ceil(2*sqrt(x^2+y^2));
    if v > N then break fi;
    if y=x or y=0 then V[v]:= V[v]+4 else V[v]:= V[v]+8 fi
od od:
ListTools:-PartialSums(convert(V,list)); # Robert Israel, Mar 29 2020