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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 1 |
| 6 | 2 |
| 7 | 5 |
| 8 | 12 |
| 9 | 29 |
| 10 | 63 |
| 11 | 146 |
| 12 | 329 |
| 13 | 722 |
| 14 | 1613 |
| 15 | 3505 |
| 16 | 7567 |
| 17 | 16119 |
| 18 | 34194 |
| 19 | 71455 |
| 20 | 148917 |
| 21 | 307432 |
| 22 | 631816 |
| 23 | 1290905 |
| 24 | 2628736 |
| 25 | 5330368 |
[0,0,0,0,1,2,5,12,29,63,146,329,722,1613,3505, 7567,16119,34194,71455,148917,307432,631816, 1290905,2628736,5330368] |