# A365554 (b-file synthesized from sequence entry)
2 2
3 10
4 60
5 396
6 2976
7 25056
8 234720
9 2423520
10 27371520
11 335819520
12 4449150720
13 63318931200
14 963548006400
15 15614378035200
16 268480048435200
17 4882321001779200
18 93627018326016000
19 1888394741194752000
20 39963486306078720000
21 885457095215616000000