[seqfan] Floor of Volume of the unit sphere in 2n-dimensional space

[Jonathan Post]

Should this be considered interesting enough for submission?
a(n) = floor( ((2*pi)^n)/(n-1)!) = integer part of Volume of the unit
sphere in 2n-dimensional space.

for positive n:

6, 39, 124, 259, 408, 512, 536, 481, 378, 264, 166, 94, 49, 24, 10, 4,
1, 0, 0, 0, 0, 0, 0, 0, 0, ....

This also occurs in the recently cited 1944 Chern proof of the
Gauss-Bonnet theorem.

n   ((2*pi)^n) / (n-1)!
1   6.28318531
2   39.4784176
3   124.025107
4   259.757576
5   408.026246
6   512.740903
7   536.941018
8   481.957131
9   378.528246
10  264.262568
11  166.041068
12  94.8424365
13  49.6593836
14  24.00147
15  10.7718345
16  4.5120955
17  1.77189576
18  0.654891141
19  0.228600133
20  0.075596684