A253217 - OEIS

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A253217 as a simple table

n	a(n)
1	0
2	0
3	1
4	19
5	268
6	3568
7	47698
8	649712
9	9023385
10	127419681
11	1823918697
12	26398702645
13	385582981615
14	5674890516295
15	84060883775765
16	1252066289632643
17	18738613233957420
18	281620474177057788
19	4248088188086420832

[0,0,1,19,268,3568,47698,649712,9023385,127419681, 1823918697,26398702645,385582981615,5674890516295, 84060883775765,1252066289632643,18738613233957420, 281620474177057788,4248088188086420832]