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A107991 as a simple table

na(n)
11
21
31
43
58
640
7180
81260
98064
1072576
11604800
126652800
1368428800
14889574400
1510897286400
16163459296000
172324754432000
1839520825344000
19640237370572800
2012164510040883200
21221172909834240000
224644631106519040000
2393666727314800640000

[1,1,1,3,8,40,180,1260,8064,72576,604800,6652800,
 68428800,889574400,10897286400,163459296000,
 2324754432000,39520825344000,640237370572800,
 12164510040883200,221172909834240000,
 4644631106519040000,93666727314800640000]