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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 9 |
| 5 | 20 |
| 6 | 47 |
| 7 | 111 |
| 8 | 270 |
| 9 | 663 |
| 10 | 1656 |
| 11 | 4174 |
| 12 | 10636 |
| 13 | 27308 |
| 14 | 70651 |
| 15 | 183902 |
| 16 | 481436 |
| 17 | 1266515 |
| 18 | 3346793 |
| 19 | 8879116 |
| 20 | 23642034 |
| 21 | 63156917 |
| 22 | 169222939 |
| 23 | 454660940 |
| 24 | 1224650739 |
| 25 | 3306338583 |
| 26 | 8945780742 |
| 27 | 24252558183 |
| 28 | 65872671839 |
| 29 | 179228552638 |
| 30 | 488443704486 |
[1,1,2,4,9,20,47,111,270,663,1656,4174,10636, 27308,70651,183902,481436,1266515,3346793,8879116, 23642034,63156917,169222939,454660940,1224650739, 3306338583,8945780742,24252558183,65872671839, 179228552638,488443704486] |