A009256 - OEIS

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A009256 as a simple table

n	a(n)
0	1
1	2
2	28
3	872
4	47248
5	3907232
6	454886848
7	70597546112
8	14042505449728
9	3475021574246912
10	1045247734061145088
11	375054668796817221632
12	158085597663328138006528
13	77269840864693331267919872

[1,2,28,872,47248,3907232,454886848,70597546112, 14042505449728,3475021574246912, 1045247734061145088,375054668796817221632, 158085597663328138006528, 77269840864693331267919872]