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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 47 |
| 5 | 272 |
| 6 | 1685 |
| 7 | 10939 |
| 8 | 73462 |
| 9 | 506111 |
| 10 | 3557109 |
| 11 | 25404296 |
| 12 | 183834627 |
| 13 | 1344987117 |
| 14 | 9932411282 |
| 15 | 73937697965 |
| 16 | 554234827675 |
| 17 | 4179895359240 |
| 18 | 31693701617841 |
| 19 | 241467983156655 |
| 20 | 1847602171074502 |
| 21 | 14191725625366331 |
| 22 | 109390959408760713 |
[0,1,2,9,47,272,1685,10939,73462,506111,3557109, 25404296,183834627,1344987117,9932411282, 73937697965,554234827675,4179895359240, 31693701617841,241467983156655,1847602171074502, 14191725625366331,109390959408760713] |