A018953 - OEIS

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A018953 as a simple table

n	a(n)
2	2
3	6
4	34
5	217
6	1092
7	6616
8	39640
9	254593
10	1678272
11	11264666
12	77021822
13	533716317
14	3728816166
15	26255378070
16	186191393010

[2,6,34,217,1092,6616,39640,254593,1678272, 11264666,77021822,533716317,3728816166, 26255378070,186191393010]

[2,6,34,217,1092,6616,39640,254593,1678272,
 11264666,77021822,533716317,3728816166,
 26255378070,186191393010]