A020114 - OEIS

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A020114 as a simple table

n	a(n)
0	1
1	1
2	1
3	1
4	1
5	4
6	18
7	105
8	741
9	6006
10	54718
11	553254
12	6147264
13	74450194
14	976124761
15	13774204959
16	208143541602
17	3353423725802
18	57380805974820
19	1039230152655058
20	19860842917407766
21	399423618672311730

[1,1,1,1,1,4,18,105,741,6006,54718,553254,6147264, 74450194,976124761,13774204959,208143541602, 3353423725802,57380805974820,1039230152655058, 19860842917407766,399423618672311730]