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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 7 |
| 4 | 20 |
| 5 | 59 |
| 6 | 185 |
| 7 | 600 |
| 8 | 2003 |
| 9 | 6833 |
| 10 | 23727 |
| 11 | 83606 |
| 12 | 298313 |
| 13 | 1076155 |
| 14 | 3920823 |
| 15 | 14416987 |
| 16 | 53482012 |
| 17 | 200151737 |
| 18 | 755894009 |
| 19 | 2882782933 |
| 20 | 11115015138 |
| 21 | 43400057683 |
| 22 | 172016505877 |
| 23 | 694208585423 |
| 24 | 2863726993748 |
| 25 | 12130698802645 |
[1,1,3,7,20,59,185,600,2003,6833,23727,83606, 298313,1076155,3920823,14416987,53482012, 200151737,755894009,2882782933,11115015138, 43400057683,172016505877,694208585423, 2863726993748,12130698802645] |