A220875 - OEIS

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A220875 as a simple table

n	a(n)
1	1
2	3
3	15
4	87
5	507
6	2859
7	15495
8	80943
9	409539
10	2015907
11	9687855
12	45574791
13	210305739
14	953479899
15	4252898199
16	18683733663

[1,3,15,87,507,2859,15495,80943,409539,2015907, 9687855,45574791,210305739,953479899,4252898199, 18683733663]