n | a(n) |
---|---|
0 | 1 |
1 | 6 |
2 | 18 |
3 | 48 |
4 | 126 |
5 | 300 |
6 | 750 |
7 | 1686 |
8 | 4074 |
9 | 8868 |
10 | 20892 |
11 | 44634 |
12 | 103392 |
13 | 216348 |
14 | 499908 |
15 | 1017780 |
16 | 2383596 |
17 | 4648470 |
18 | 11271102 |
19 | 20763036 |
20 | 52671018 |
21 | 91377918 |
[1,6,18,48,126,300,750,1686,4074,8868,20892,44634, 103392,216348,499908,1017780,2383596,4648470, 11271102,20763036,52671018,91377918] |