A020079 - OEIS

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A020079 as a simple table

n	a(n)
0	1
1	0
2	0
3	0
4	1
5	4
6	23
7	143
8	1027
9	8370
10	76527
11	776207
12	8649165
13	105025575
14	1380336141
15	19521896861
16	295617295326
17	4772107767405
18	81807561726950
19	1484222905617529
20	28412267050392705
21	572304236300767347

[1,0,0,0,1,4,23,143,1027,8370,76527,776207, 8649165,105025575,1380336141,19521896861, 295617295326,4772107767405,81807561726950, 1484222905617529,28412267050392705, 572304236300767347]