n | a(n) |
---|---|
0 | 0 |
1 | 0 |
2 | 2 |
3 | 4 |
4 | 7 |
5 | 20 |
6 | 72 |
7 | 240 |
8 | 722 |
9 | 2140 |
10 | 6508 |
11 | 20077 |
12 | 61776 |
13 | 189056 |
14 | 577856 |
15 | 1768380 |
16 | 5416230 |
17 | 16587984 |
18 | 50788707 |
19 | 155489884 |
20 | 476058864 |
21 | 1457605616 |
22 | 4462928950 |
23 | 13664497400 |
24 | 41837412392 |
25 | 128096408137 |
26 | 392202398144 |
27 | 1200835918016 |
28 | 3676688064688 |
[0,0,2,4,7,20,72,240,722,2140,6508,20077,61776, 189056,577856,1768380,5416230,16587984,50788707, 155489884,476058864,1457605616,4462928950, 13664497400,41837412392,128096408137,392202398144, 1200835918016,3676688064688] |