A019613 - OEIS

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A019613 as a simple table

n	a(n)
0	1
1	20
2	273
3	3172
4	33809
5	342132
6	3348241
7	32033924
8	301669137
9	2808831124
10	25937190929
11	238042888356
12	2174659962385
13	19797924540596
14	179763483454737
15	1628947562960068
16	14738065844679953
17	133185374228264148

[1,20,273,3172,33809,342132,3348241,32033924, 301669137,2808831124,25937190929,238042888356, 2174659962385,19797924540596,179763483454737, 1628947562960068,14738065844679953, 133185374228264148]