A208421 - OEIS

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A208421 as a simple table

n	a(n)
1	9
2	81
3	261
4	1269
5	5139
6	22509
7	95265
8	409239
9	1746639
10	7475751
11	31957515
12	136685781
13	584484003
14	2499573411
15	10689072525
16	45711185121
17	195479542125
18	835952734845
19	3574879817931
20	15287675934645
21	65376453864249

[9,81,261,1269,5139,22509,95265,409239,1746639, 7475751,31957515,136685781,584484003,2499573411, 10689072525,45711185121,195479542125,835952734845, 3574879817931,15287675934645,65376453864249]