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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 7 |
| 5 | 21 |
| 6 | 64 |
| 7 | 204 |
| 8 | 666 |
| 9 | 2236 |
| 10 | 7625 |
| 11 | 26419 |
| 12 | 92644 |
| 13 | 328370 |
| 14 | 1174234 |
| 15 | 4231898 |
| 16 | 15354424 |
| 17 | 56042372 |
| 18 | 205626906 |
| 19 | 758021598 |
| 20 | 2806143522 |
| 21 | 10427671924 |
| 22 | 38882984840 |
| 23 | 145443260702 |
| 24 | 545598228056 |
| 25 | 2052086677666 |
| 26 | 7736986142773 |
| 27 | 29236241424977 |
[1,1,1,3,7,21,64,204,666,2236,7625,26419,92644, 328370,1174234,4231898,15354424,56042372, 205626906,758021598,2806143522,10427671924, 38882984840,145443260702,545598228056, 2052086677666,7736986142773,29236241424977] |