sub f {
#23456789012345678901234567890123456789012345678901234567890123456789012345678901
my$x=my$i=pop;$x?([1..$x],map[(map$_+2*$x-1,reverse@$_),++$i],reverse f($x-1)):()
}

##</code><code>##

## print "@$_\n" for f(5);
1 2 3 4 5
16 17 18 19 6
15 24 25 20 7
14 23 22 21 8
13 12 11 10 9

##</code><code>##

 +---------------+
 | 1 2 3 ...  n  |
 | +-------+ n+1 |
 | |       |  .  |
 | |  ***  |  .  |
 | |       |  .  |
 | +-------+ 2n-1|
 +---------------+