A178704 - OEIS

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A178704 as a simple table

n	a(n)
0	0
1	0
2	1
3	4
4	15
5	49
6	153
7	465
8	1402
9	4213
10	12648
11	37954
12	113874
13	341634
14	1024915
15	3074758
16	9224289
17	27672883
18	83018667
19	249056019
20	747168076
21	2241504247
22	6724512762
23	20173538308
24	60520614948
25	181561844868

[0,0,1,4,15,49,153,465,1402,4213,12648,37954, 113874,341634,1024915,3074758,9224289,27672883, 83018667,249056019,747168076,2241504247, 6724512762,20173538308,60520614948,181561844868]