n | a(n) |
---|---|
0 | 1 |
1 | 4 |
2 | 12 |
3 | 40 |
4 | 140 |
5 | 504 |
6 | 1848 |
7 | 6864 |
8 | 25740 |
9 | 97240 |
10 | 369512 |
11 | 1410864 |
12 | 5408312 |
13 | 20801200 |
14 | 80233200 |
15 | 310235040 |
16 | 1202160780 |
17 | 4667212440 |
18 | 18150270600 |
19 | 70690527600 |
20 | 275693057640 |
21 | 1076515748880 |
22 | 4208197927440 |
23 | 16466861455200 |
24 | 64495207366200 |
25 | 252821212875504 |
26 | 991837065896208 |
[1,4,12,40,140,504,1848,6864,25740,97240,369512, 1410864,5408312,20801200,80233200,310235040, 1202160780,4667212440,18150270600,70690527600, 275693057640,1076515748880,4208197927440, 16466861455200,64495207366200,252821212875504, 991837065896208] |