# A153299 (b-file synthesized from sequence entry)
0 1
1 1
2 4
3 20
4 111
5 657
6 4067
7 26028
8 170913
9 1145446
10 7804797
11 53911104
12 376669462
13 2657391772
14 18904566514
15 135460704648
16 976795422828
17 7082951967141
18 51614974500605
19 377798933519164
20 2776363089297553
21 20476554379564305