A030838 - OEIS

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A030838 as a simple table

n	a(n)
1	1
2	2
3	6
4	27
5	137
6	825
7	5776
8	46210
9	415896
10	4158962
11	45748587
12	548983054
13	7136779702
14	99914915833
15	1498723737508
16	23979579800136
17	407652856602324
18	7337751418841832
19	139417276957994821
20	2788345539159896420

[1,2,6,27,137,825,5776,46210,415896,4158962, 45748587,548983054,7136779702,99914915833, 1498723737508,23979579800136,407652856602324, 7337751418841832,139417276957994821, 2788345539159896420]