A039831 - OEIS

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A039831 as a simple table

n	a(n)
1	1
2	2
3	4
4	13
5	57
6	315
7	2057
8	15484
9	132317
10	1261560
11	13281295
12	153218597
13	1921565205
14	26008169266
15	377922606876
16	5871153031163
17	97096594212804
18	1702487540383101
19	31551431772637772
20	616331122530164638

[1,2,4,13,57,315,2057,15484,132317,1261560, 13281295,153218597,1921565205,26008169266, 377922606876,5871153031163,97096594212804, 1702487540383101,31551431772637772, 616331122530164638]