n | a(n) |
---|---|
0 | 1 |
1 | 1 |
2 | 4 |
3 | 18 |
4 | 90 |
5 | 481 |
6 | 2690 |
7 | 15547 |
8 | 92124 |
9 | 556664 |
10 | 3417062 |
11 | 21248966 |
12 | 133576724 |
13 | 847465593 |
14 | 5419399722 |
15 | 34895368578 |
16 | 226050057378 |
17 | 1472170887755 |
18 | 9633297762870 |
19 | 63305402213336 |
20 | 417612181048826 |
21 | 2764492667188504 |
22 | 18358282050480384 |
23 | 122265756020847943 |
[1,1,4,18,90,481,2690,15547,92124,556664,3417062, 21248966,133576724,847465593,5419399722, 34895368578,226050057378,1472170887755, 9633297762870,63305402213336,417612181048826, 2764492667188504,18358282050480384, 122265756020847943] |