A128321 - OEIS

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A128321 as a simple table

n	a(n)
0	1
1	1
2	4
3	17
4	98
5	622
6	4512
7	35373
8	300974
9	2722070
10	26118056
11	263266346
12	2780054884
13	30586452652
14	349724463584
15	4141218303165
16	50678688359190
17	639387728054310
18	8302396672724280
19	110754894628585950

[1,1,4,17,98,622,4512,35373,300974,2722070, 26118056,263266346,2780054884,30586452652, 349724463584,4141218303165,50678688359190, 639387728054310,8302396672724280, 110754894628585950]