A026089 - OEIS

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A026089 as a simple table

n	a(n)
0	1
1	2
2	4
3	16
4	93
5	518
6	2932
7	16709
8	95849
9	552749
10	3201848
11	18616751
12	108592239
13	635175153
14	3724193120
15	21881993115
16	128810517855
17	759515272026
18	4485048436792
19	26520334731436
20	157006248094198

[1,2,4,16,93,518,2932,16709,95849,552749,3201848, 18616751,108592239,635175153,3724193120, 21881993115,128810517855,759515272026, 4485048436792,26520334731436,157006248094198]