n | a(n) |
---|---|
1 | 0 |
2 | 1 |
3 | 4 |
4 | 19 |
5 | 54 |
6 | 180 |
7 | 508 |
8 | 1533 |
9 | 4332 |
10 | 13041 |
11 | 37492 |
12 | 111367 |
13 | 326636 |
14 | 968802 |
15 | 2858460 |
16 | 8483290 |
17 | 25113618 |
18 | 74512947 |
19 | 220885446 |
20 | 655274837 |
21 | 1943117294 |
22 | 5763235194 |
23 | 17089323366 |
24 | 50673594159 |
25 | 150232437482 |
26 | 445359235627 |
27 | 1320070201468 |
[0,1,4,19,54,180,508,1533,4332,13041,37492,111367, 326636,968802,2858460,8483290,25113618,74512947, 220885446,655274837,1943117294,5763235194, 17089323366,50673594159,150232437482,445359235627, 1320070201468] |