A020130 - OEIS

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A020130 as a simple table

n	a(n)
0	1
1	1
2	1
3	1
4	2
5	8
6	37
7	229
8	1648
9	13508
10	124269
11	1267543
12	14196478
13	173197025
14	2286200719
15	32464050200
16	493453563030
17	7993947721072
18	137495900802424
19	2502425394604114
20	48046567576398987
21	970540665043259526

[1,1,1,1,2,8,37,229,1648,13508,124269,1267543, 14196478,173197025,2286200719,32464050200, 493453563030,7993947721072,137495900802424, 2502425394604114,48046567576398987, 970540665043259526]