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A180119 as a simple table

na(n)
00
11
26
336
4240
51800
615120
7141120
81451520
916329600
10199584000
112634508800
1237362124800
13566658892800
149153720576000
15156920924160000
162845499424768000
1754420176498688000
181094805903679488000
1923112569077678080000
20510909421717094400000
2111802007641664880640000

[0,1,6,36,240,1800,15120,141120,1451520,16329600,
 199584000,2634508800,37362124800,566658892800,
 9153720576000,156920924160000,2845499424768000,
 54420176498688000,1094805903679488000,
 23112569077678080000,510909421717094400000,
 11802007641664880640000]