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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 9 |
| 3 | 36 |
| 4 | 164 |
| 5 | 505 |
| 6 | 2474 |
| 7 | 7273 |
| 8 | 31008 |
| 9 | 103644 |
| 10 | 379890 |
| 11 | 1226802 |
| 12 | 4747529 |
| 13 | 14553648 |
| 14 | 52167558 |
| 15 | 171639695 |
| 16 | 583371802 |
| 17 | 1851395692 |
| 18 | 6427705062 |
| 19 | 19983302144 |
| 20 | 67235043192 |
| 21 | 214615427776 |
| 22 | 697704303005 |
| 23 | 2194982897304 |
| 24 | 7262755260410 |
| 25 | 22402942281766 |
| 26 | 72461661415093 |
[1,1,9,36,164,505,2474,7273,31008,103644,379890, 1226802,4747529,14553648,52167558,171639695, 583371802,1851395692,6427705062,19983302144, 67235043192,214615427776,697704303005, 2194982897304,7262755260410,22402942281766, 72461661415093] |