A080108 - OEIS

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A080108 as a simple table

n	a(n)
1	1
2	2
3	6
4	23
5	104
6	537
7	3100
8	19693
9	136064
10	1013345
11	8076644
12	68486013
13	614797936
14	5818490641
15	57846681092
16	602259154853
17	6548439927680
18	74180742421185
19	873588590481988
20	10674437936521069
21	135097459659312176

[1,2,6,23,104,537,3100,19693,136064,1013345, 8076644,68486013,614797936,5818490641,57846681092, 602259154853,6548439927680,74180742421185, 873588590481988,10674437936521069, 135097459659312176]