A053592 - OEIS

%I #9 Mar 23 2022 12:18:15

%S 0,1,1,19,27,81,93,179,251,389,485,739,895,1189,1365,1791,2103,2553,

%T 2969,3695,4139,4945,5497,6403,7123,8217,9093,10395,11459,12893,13997,

%U 15515,17071,18853,20377,22575,24303,26745,28545,31103,33371

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

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

%K easy,nonn

%O 0,4

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