# A103771 (b-file synthesized from sequence entry)
0 1
1 4
2 20
3 100
4 496
5 2464
6 12240
7 60800
8 302016
9 1500224
10 7452160
11 37017600
12 183879936
13 913398784
14 4537185280
15 22537856000
16 111953760256
17 556115206144
18 2762427289600
19 13721985024000
20 68162110078976
21 338586089570304