A155661 - OEIS

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A155661 as a simple table

n	a(n)
0	1
1	4
2	52
3	658
4	7600
5	83194
6	882352
7	9176458
8	94235200
9	959646394
10	9717524752
11	98022673258
12	986158712800
13	9903110989594
14	99321776927152
15	995252438490058
16	9966767069430400
17	99767369486012794
18	998371586402089552

[1,4,52,658,7600,83194,882352,9176458,94235200, 959646394,9717524752,98022673258,986158712800, 9903110989594,99321776927152,995252438490058, 9966767069430400,99767369486012794, 998371586402089552]