A026859 - OEIS

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A026859 as a simple table

n	a(n)
4	1
5	15
6	141
7	1070
8	7187
9	44673
10	263431
11	1496218
12	8266100
13	44718596
14	238015318
15	1250656153
16	6504202391
17	33543967700
18	171810543570
19	875006817465
20	4435130657170
21	22390449598704
22	112654298838120
23	565172299571352

[1,15,141,1070,7187,44673,263431,1496218,8266100, 44718596,238015318,1250656153,6504202391, 33543967700,171810543570,875006817465, 4435130657170,22390449598704,112654298838120, 565172299571352]