n | a(n) |
---|---|
0 | 0 |
1 | 1 |
2 | 2 |
3 | 6 |
4 | 18 |
5 | 45 |
6 | 102 |
7 | 213 |
8 | 426 |
9 | 821 |
10 | 1538 |
11 | 2820 |
12 | 5075 |
13 | 8996 |
14 | 15743 |
15 | 27247 |
16 | 46709 |
17 | 79405 |
18 | 133996 |
19 | 224640 |
20 | 374400 |
[0,1,2,6,18,45,102,213,426,821,1538,2820,5075, 8996,15743,27247,46709,79405,133996,224640,374400] |