A037781 - OEIS

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A037781 as a simple table

n	a(n)
1	3
2	19
3	116
4	696
5	4179
6	25075
7	150452
8	902712
9	5416275
10	32497651
11	194985908
12	1169915448
13	7019492691
14	42116956147
15	252701736884
16	1516210421304
17	9097262527827
18	54583575166963
19	327501451001780
20	1965008706010680

[3,19,116,696,4179,25075,150452,902712,5416275, 32497651,194985908,1169915448,7019492691, 42116956147,252701736884,1516210421304, 9097262527827,54583575166963,327501451001780, 1965008706010680]