A331685 - OEIS

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A331685 as a simple table

n	a(n)
1	1
2	3
3	7
4	23
5	69
6	261
7	943
8	3815
9	15107
10	63219
11	262791
12	1130953
13	4838813
14	21185125
15	92593943
16	411160627
17	1823656199
18	8186105099
19	36728532951
20	166310761655

[1,3,7,23,69,261,943,3815,15107,63219,262791, 1130953,4838813,21185125,92593943,411160627, 1823656199,8186105099,36728532951,166310761655]