n | a(n) |
---|---|
0 | 0 |
1 | 1 |
2 | 4 |
3 | 21 |
4 | 104 |
5 | 521 |
6 | 2604 |
7 | 13021 |
8 | 65104 |
9 | 325521 |
10 | 1627604 |
11 | 8138021 |
12 | 40690104 |
13 | 203450521 |
14 | 1017252604 |
15 | 5086263021 |
16 | 25431315104 |
17 | 127156575521 |
18 | 635782877604 |
19 | 3178914388021 |
20 | 15894571940104 |
21 | 79472859700521 |
[0,1,4,21,104,521,2604,13021,65104,325521,1627604, 8138021,40690104,203450521,1017252604,5086263021, 25431315104,127156575521,635782877604, 3178914388021,15894571940104,79472859700521] |