A056474 - OEIS

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A056474 as a simple table

n	a(n)
1	0
2	0
3	0
4	0
5	0
6	0
7	0
8	0
9	1
10	1
11	15
12	15
13	140
14	140
15	1050
16	1050
17	6951
18	6951
19	42525
20	42525
21	246730
22	246730
23	1379400
24	1379400
25	7508501
26	7508501
27	40075035
28	40075035
29	210766920
30	210766920
31	1096190550

[0,0,0,0,0,0,0,0,1,1,15,15,140,140,1050,1050,6951, 6951,42525,42525,246730,246730,1379400,1379400, 7508501,7508501,40075035,40075035,210766920, 210766920,1096190550]