A166899 - OEIS

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A166899 as a simple table

n	a(n)
1	1
2	3
3	25
4	111
5	456
6	2697
7	15961
8	86247
9	495781
10	3003738
11	17946798
12	107667969
13	660458787
14	4081397547
15	25274724105
16	157744019799
17	991384251102
18	6254115981009
19	39613066988527
20	252017709962526
21	1608980424431755

[1,3,25,111,456,2697,15961,86247,495781,3003738, 17946798,107667969,660458787,4081397547, 25274724105,157744019799,991384251102, 6254115981009,39613066988527,252017709962526, 1608980424431755]