A107872 - OEIS

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A107872 as a simple table

n	a(n)
0	1
1	4
2	21
3	165
4	1820
5	26334
6	475020
7	10295472
8	260932815
9	7575968400
10	247994680648
11	9036996468045
12	362827605867363
13	15913388077274800
14	757000487505568680
15	38819452599736372800
16	2134712294190092847615

[1,4,21,165,1820,26334,475020,10295472,260932815, 7575968400,247994680648,9036996468045, 362827605867363,15913388077274800, 757000487505568680,38819452599736372800, 2134712294190092847615]