n | a(n) |
---|---|
0 | 1 |
1 | 1 |
2 | 2 |
3 | 4 |
4 | 9 |
5 | 21 |
6 | 51 |
7 | 126 |
8 | 321 |
9 | 820 |
10 | 2160 |
11 | 5654 |
12 | 15272 |
13 | 40758 |
14 | 112280 |
15 | 304471 |
16 | 852164 |
17 | 2341980 |
18 | 6640755 |
19 | 18460066 |
20 | 52915999 |
[1,1,2,4,9,21,51,126,321,820,2160,5654,15272, 40758,112280,304471,852164,2341980,6640755, 18460066,52915999] |