A113947 - OEIS

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A113947 as a simple table

n	a(n)
1	1
2	2
3	3
4	8
5	16
6	64
7	264
8	1580
9	10648
10	84320
11	750380
12	7455312
13	81566928
14	974988768
15	12636692720
16	176505029160
17	2642791002368
18	42224138928712
19	716984262871596
20	12893605560786944

[1,2,3,8,16,64,264,1580,10648,84320,750380, 7455312,81566928,974988768,12636692720, 176505029160,2642791002368,42224138928712, 716984262871596,12893605560786944]