A222981 - OEIS

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A222981 as a simple table

n	a(n)
1	1
2	7
3	43
4	584
5	2903
6	45718
7	227569
8	3706702
9	18721501
10	309335666
11	1578160193
12	26302908158
13	135163043693
14	2266015930226
15	11706886012409
16	197109806616950
17	1022513778146405
18	17272771472939290
19	89894465367630385

[1,7,43,584,2903,45718,227569,3706702,18721501, 309335666,1578160193,26302908158,135163043693, 2266015930226,11706886012409,197109806616950, 1022513778146405,17272771472939290, 89894465367630385]