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A000090 as a simple table

na(n)
01
11
22
34
416
580
6520
73640
829120
9259840
102598400
1128582400
12343235200
134462057600
1462468806400
15936987251200
1614991796019200
17254860532326400
184587501779660800
1987162533813555200
201743250676271104000
2136608259566534656000
22805381710463762432000

[1,1,2,4,16,80,520,3640,29120,259840,2598400,
 28582400,343235200,4462057600,62468806400,
 936987251200,14991796019200,254860532326400,
 4587501779660800,87162533813555200,
 1743250676271104000,36608259566534656000,
 805381710463762432000]