A155668 - OEIS

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A155668 as a simple table

n	a(n)
0	1
1	4
2	58
3	820
4	10546
5	128284
6	1509418
7	17390020
8	197581666
9	2223729964
10	24863682778
11	276721736020
12	3069708899986
13	33972956330044
14	375351787072138
15	4142063797326820
16	45668254886861506
17	503195228685608524

[1,4,58,820,10546,128284,1509418,17390020, 197581666,2223729964,24863682778,276721736020, 3069708899986,33972956330044,375351787072138, 4142063797326820,45668254886861506, 503195228685608524]