Information bits in permutations

perl -lwe 'for $i ( 1 .. 10 ) { for $j ( 1 , $i .. $i + 3 ) { $v = $i * $j ; $s = 0 ; for ( 1 .. $v ) { $s += log ( $_ ) } $s /= log ( 2 ) ; print "$v $s" } }' | sort -nu

1	0
2	1
3	2.58496250072116
4	4.58496250072116
5	6.90689059560852
6	9.49185309632968
7	12.2992080183873
8	15.2992080183873
9	18.4691330198296
10	21.791061114717
12	28.8354552340754
15	40.2501404698826
16	44.2501404698826
18	52.5075283125753
20	61.0773839209062
24	79.0376574191005
25	83.6815136088752
28	97.9441957512373
30	107.709067341973
35	132.924403629914
36	138.094328631356
40	159.159039824179
42	169.908909251575
48	202.9495720297
49	208.564281873815
54	237.063811080429
56	248.652525716012
63	289.995143941724