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A091549 as a simple table

na(n)
21
328
4960
543200
62520000
7186278400
817069875200
91902071808000
10253487646720000
1139833773056000000
127291173820170240000
131538106259064094720000
14370502654756909875200000

[1,28,960,43200,2520000,186278400,17069875200,
 1902071808000,253487646720000,39833773056000000,
 7291173820170240000,1538106259064094720000,
 370502654756909875200000]