n | a(n) |
---|---|
1 | 0 |
2 | 2 |
3 | 4 |
4 | 20 |
5 | 86 |
6 | 424 |
7 | 2128 |
8 | 11200 |
9 | 60372 |
10 | 333254 |
11 | 1872728 |
12 | 10688284 |
13 | 61792756 |
14 | 361247006 |
15 | 2132290212 |
16 | 12692489494 |
17 | 76115308712 |
18 | 459476777038 |
19 | 2790092370660 |
20 | 17032567789840 |
21 | 104478722395496 |
22 | 643682329681246 |
23 | 3981493201581658 |
[0,2,4,20,86,424,2128,11200,60372,333254,1872728, 10688284,61792756,361247006,2132290212, 12692489494,76115308712,459476777038, 2790092370660,17032567789840,104478722395496, 643682329681246,3981493201581658] |