login

Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.

Open 3-dimensional ball numbers (version 3): a(n) is the number of integer points (i,j,k) contained in an open ball of diameter n, centered at (1/2,1/2,0).
0

%I #8 Mar 23 2022 12:51:19

%S 0,0,4,12,36,56,112,168,268,372,536,680,888,1132,1452,1740,2160,2544,

%T 3048,3556,4196,4812,5552,6304,7248,8116,9220,10280,11512,12656,14108,

%U 15564,17164,18800,20664,22368,24436,26412,28692,30984,33536

%N Open 3-dimensional ball numbers (version 3): a(n) is the number of integer points (i,j,k) contained in an open ball of diameter n, centered at (1/2,1/2,0).

%C a(n)/(n/2)^3 -> (4/3)*Pi.

%K easy,nonn

%O 0,3

%A Klaus Strassburger (strass(AT)ddfi.uni-duesseldorf.de), Jan 19 2000