n | a(n) |
---|---|
0 | -1 |
1 | -1 |
2 | 0 |
3 | 3 |
4 | 12 |
5 | 40 |
6 | 130 |
7 | 427 |
8 | 1428 |
9 | 4860 |
10 | 16794 |
11 | 58784 |
12 | 208010 |
13 | 742898 |
14 | 2674438 |
15 | 9694843 |
16 | 35357668 |
17 | 129644788 |
18 | 477638698 |
19 | 1767263188 |
20 | 6564120418 |
21 | 24466267018 |
22 | 91482563638 |
23 | 343059613648 |
24 | 1289904147322 |
25 | 4861946401450 |
26 | 18367353072150 |
27 | 69533550916002 |
28 | 263747951750358 |
[-1,-1,0,3,12,40,130,427,1428,4860,16794,58784, 208010,742898,2674438,9694843,35357668,129644788, 477638698,1767263188,6564120418,24466267018, 91482563638,343059613648,1289904147322, 4861946401450,18367353072150,69533550916002, 263747951750358] |