A002221 - OEIS

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A002221 as a simple table

n	a(n)
1	1
2	5
3	15
4	55
5	140
6	448
7	1022
8	2710
9	6048
10	14114
11	28831
12	64091
13	123649
14	251295
15	476835
16	916972
17	1654044
18	3080159
19	5377431
20	9624588
21	16490017
22	28433473
23	47423409
24	80279375

[1,5,15,55,140,448,1022,2710,6048,14114,28831, 64091,123649,251295,476835,916972,1654044,3080159, 5377431,9624588,16490017,28433473,47423409, 80279375]