| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 9 |
| 5 | 20 |
| 6 | 48 |
| 7 | 116 |
| 8 | 288 |
| 9 | 724 |
| 10 | 1849 |
| 11 | 4768 |
| 12 | 12423 |
| 13 | 32628 |
| 14 | 86342 |
| 15 | 229952 |
| 16 | 616042 |
| 17 | 1659012 |
| 18 | 4489101 |
| 19 | 12199521 |
| 20 | 33284546 |
| 21 | 91140797 |
| 22 | 250396629 |
| 23 | 690043032 |
| 24 | 1907022197 |
| 25 | 5284167884 |
| 26 | 14677681554 |
| 27 | 40862469713 |
| 28 | 114001697975 |
[1,1,2,4,9,20,48,116,288,724,1849,4768,12423, 32628,86342,229952,616042,1659012,4489101, 12199521,33284546,91140797,250396629,690043032, 1907022197,5284167884,14677681554,40862469713, 114001697975] |