| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 8 |
| 3 | 30 |
| 4 | 108 |
| 5 | 378 |
| 6 | 1296 |
| 7 | 4374 |
| 8 | 14580 |
| 9 | 48114 |
| 10 | 157464 |
| 11 | 511758 |
| 12 | 1653372 |
| 13 | 5314410 |
| 14 | 17006112 |
| 15 | 54206982 |
| 16 | 172186884 |
| 17 | 545258466 |
| 18 | 1721868840 |
| 19 | 5423886846 |
| 20 | 17046501516 |
| 21 | 53464027482 |
| 22 | 167365651248 |
| 23 | 523017660150 |
| 24 | 1631815099668 |
| 25 | 5083731656658 |
| 26 | 15816054042936 |
[1,2,8,30,108,378,1296,4374,14580,48114,157464, 511758,1653372,5314410,17006112,54206982, 172186884,545258466,1721868840,5423886846, 17046501516,53464027482,167365651248,523017660150, 1631815099668,5083731656658,15816054042936] |