A338531 - OEIS

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A338531 as a simple table

n	a(n)
1	1
2	4
3	16
4	61
5	225
6	815
7	2923
8	10428
9	37097
10	131776
11	467732
12	1659537
13	5886945
14	20880912
15	74060619
16	262672473
17	931615218
18	3304121816
19	11718561425
20	41561571533

[1,4,16,61,225,815,2923,10428,37097,131776,467732, 1659537,5886945,20880912,74060619,262672473, 931615218,3304121816,11718561425,41561571533]