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A081406 as a simple table

na(n)
01
11
21
34
45
56
628
740
854
9280
10440
11648
123640
136160
149720
1558240
16104720
17174960
181106560
192094400
203674160
2124344320
2248171200
2388179840
24608608000
251252451200
262380855680
2717041024000
2836321084800
2971425670400
30528271744000
311162274713600

[1,1,1,4,5,6,28,40,54,280,440,648,3640,6160,9720,
 58240,104720,174960,1106560,2094400,3674160,
 24344320,48171200,88179840,608608000,1252451200,
 2380855680,17041024000,36321084800,71425670400,
 528271744000,1162274713600]