A235532 a(n) = floor(n^2 * (4-Pi)).

0, 0, 3, 7, 13, 21, 30, 42, 54, 69, 85, 103, 123, 145, 168, 193, 219, 248, 278, 309, 343, 378, 415, 454, 494, 536, 580, 625, 672, 721, 772, 824, 879, 934, 992, 1051, 1112, 1175, 1239, 1305, 1373, 1442, 1514, 1587, 1661, 1738, 1816, 1896, 1977, 2061, 2146, 2232, 2321

Offset: 0

Author

Alex Ratushnyak, Jan 11 2014

Keywords

• nonn

Comments

a(n) = floor(As(n) - Ac(n)), where Ac(n) is the area of the circle of radius n, and As(n) is the area of square with side length 2n.

Crossrefs

Cf. A066643, A057672, A000290.

Programs

Mathematica

Floor[(4-Pi)#^2]&/@Range[0,60] (* Harvey P. Dale, Jan 10 2020 *)

Python

import math
for n in range(77): print(str(int(n*n*(4-math.pi))), end=',')