n | a(n) |
---|---|
1 | 0 |
2 | 0 |
3 | 3 |
4 | 18 |
5 | 78 |
6 | 273 |
7 | 921 |
8 | 2916 |
9 | 9150 |
10 | 28065 |
11 | 85773 |
12 | 259848 |
13 | 785778 |
14 | 2367813 |
15 | 7128201 |
16 | 21427956 |
17 | 64382550 |
18 | 193326105 |
19 | 580372293 |
20 | 1741847328 |
21 | 5227116378 |
22 | 15684323853 |
23 | 47059266081 |
24 | 141189861996 |
[0,0,3,18,78,273,921,2916,9150,28065,85773,259848, 785778,2367813,7128201,21427956,64382550, 193326105,580372293,1741847328,5227116378, 15684323853,47059266081,141189861996] |