n | a(n) |
---|---|
0 | 0 |
1 | 4 |
2 | 20 |
3 | 116 |
4 | 660 |
5 | 3764 |
6 | 21460 |
7 | 122356 |
8 | 697620 |
9 | 3977524 |
10 | 22678100 |
11 | 129300596 |
12 | 737215380 |
13 | 4203279284 |
14 | 23965257940 |
15 | 136639406836 |
16 | 779058065940 |
17 | 4441847957044 |
18 | 25325472048980 |
19 | 144394752073076 |
20 | 823275648561300 |
21 | 4693957251098804 |
22 | 26762888849739220 |
[0,4,20,116,660,3764,21460,122356,697620,3977524, 22678100,129300596,737215380,4203279284, 23965257940,136639406836,779058065940, 4441847957044,25325472048980,144394752073076, 823275648561300,4693957251098804, 26762888849739220] |