A090581 - OEIS

A090581 as a simple table

n	a(n)
1	1
2	6
3	21
4	56
5	126
6	252
7	462
8	792
9	1287
10	2001
11	2992
12	4317
13	6027
14	8162
15	10746
16	13782
17	17247
18	21087
19	25212
20	29496
21	33787
22	37917
23	41712
24	45002
25	47631
26	49467
27	50412
28	50412
29	49467
30	47631
31	45002
32	41712
33	37917
34	33787
35	29496
36	25212
37	21087
38	17247
39	13782
40	10746
41	8162
42	6027
43	4317
44	2992
45	2001
46	1287
47	792
48	462
49	252
50	126
51	56
52	21
53	6
54	1

[1,6,21,56,126,252,462,792,1287,2001,2992,4317, 6027,8162,10746,13782,17247,21087,25212,29496, 33787,37917,41712,45002,47631,49467,50412,50412, 49467,47631,45002,41712,37917,33787,29496,25212, 21087,17247,13782,10746,8162,6027,4317,2992,2001, 1287,792,462,252,126,56,21,6,1]