A105668 - OEIS

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A105668 as a simple table

n	a(n)
6	1
7	3
8	12
9	59
10	325
11	1875
12	11029
13	65607
14	393750
15	2382084
16	14517939
17	89091558
18	550217901
19	3418171915
20	21351207168

[1,3,12,59,325,1875,11029,65607,393750,2382084, 14517939,89091558,550217901,3418171915, 21351207168]