A121580 - OEIS

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A121580 as a simple table

n	a(n)
1	1
2	3
3	11
4	53
5	317
6	2237
7	18077
8	164237
9	1656077
10	18348557
11	221561357
12	2895986957
13	40737113357
14	613623026957
15	9854521894157
16	168083120422157
17	3034505335078157
18	57810369261862157
19	1159018646647078157

[1,3,11,53,317,2237,18077,164237,1656077,18348557, 221561357,2895986957,40737113357,613623026957, 9854521894157,168083120422157,3034505335078157, 57810369261862157,1159018646647078157]