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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 11 |
| 5 | 35 |
| 6 | 108 |
| 7 | 380 |
| 8 | 1348 |
| 9 | 5014 |
| 10 | 18223 |
| 11 | 67634 |
| 12 | 252849 |
| 13 | 950346 |
| 14 | 3602437 |
| 15 | 13697333 |
| 16 | 52293534 |
| 17 | 200399576 |
| 18 | 770410271 |
| 19 | 2970369338 |
| 20 | 11482572252 |
| 21 | 44492417777 |
| 22 | 172766286339 |
| 23 | 672186167762 |
| 24 | 2619985274260 |
| 25 | 10228841840226 |
| 26 | 39996338183554 |
| 27 | 156612016049122 |
[0,1,3,11,35,108,380,1348,5014,18223,67634,252849, 950346,3602437,13697333,52293534,200399576, 770410271,2970369338,11482572252,44492417777, 172766286339,672186167762,2619985274260, 10228841840226,39996338183554,156612016049122] |