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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 9 |
| 3 | 45 |
| 4 | 201 |
| 5 | 819 |
| 6 | 3357 |
| 7 | 13329 |
| 8 | 52215 |
| 9 | 199686 |
| 10 | 750733 |
| 11 | 2774793 |
| 12 | 10112184 |
| 13 | 36357280 |
| 14 | 129131448 |
| 15 | 453379226 |
| 16 | 1574884565 |
| 17 | 5415956550 |
| 18 | 18450934294 |
| 19 | 62303210591 |
| 20 | 208624947952 |
| 21 | 693066815809 |
| 22 | 2285129922950 |
| 23 | 7480504628754 |
| 24 | 24320897894515 |
| 25 | 78557786077315 |
[1,1,9,45,201,819,3357,13329,52215,199686,750733, 2774793,10112184,36357280,129131448,453379226, 1574884565,5415956550,18450934294,62303210591, 208624947952,693066815809,2285129922950, 7480504628754,24320897894515,78557786077315] |