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A053508 as a simple table

na(n)
10
20
30
41
520
6360
76860
8143360
93306744
1084000000
112338460520
1270946979840
132332989862060
1482726831323136
153148511132812500
16128071114403348480
175546563698427324720
18254873089955815096320
1912387799656377835411984

[0,0,0,1,20,360,6860,143360,3306744,84000000,
 2338460520,70946979840,2332989862060,
 82726831323136,3148511132812500,
 128071114403348480,5546563698427324720,
 254873089955815096320,12387799656377835411984]