n | a(n) |
---|---|
0 | 1 |
1 | 4 |
2 | 20 |
3 | 84 |
4 | 404 |
5 | 1748 |
6 | 8212 |
7 | 36180 |
8 | 167572 |
9 | 746452 |
10 | 3427604 |
11 | 15370836 |
12 | 70212500 |
13 | 316145876 |
14 | 1439545876 |
15 | 6497879892 |
16 | 29530613908 |
17 | 133496692180 |
18 | 605986514708 |
19 | 2741933589588 |
20 | 12437717824916 |
21 | 56308655258324 |
22 | 255312140456980 |
[1,4,20,84,404,1748,8212,36180,167572,746452, 3427604,15370836,70212500,316145876,1439545876, 6497879892,29530613908,133496692180,605986514708, 2741933589588,12437717824916,56308655258324, 255312140456980] |