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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 13 |
| 4 | 63 |
| 5 | 306 |
| 6 | 1473 |
| 7 | 7085 |
| 8 | 34239 |
| 9 | 166459 |
| 10 | 813618 |
| 11 | 3994200 |
| 12 | 19678233 |
| 13 | 97239130 |
| 14 | 481740885 |
| 15 | 2392004853 |
| 16 | 11900655999 |
| 17 | 59312062026 |
| 18 | 296071376307 |
| 19 | 1479998924447 |
| 20 | 7407613846698 |
| 21 | 37118966710076 |
| 22 | 186195636158436 |
| 23 | 934889598483048 |
| 24 | 4698229684691913 |
| 25 | 23629859054461331 |
[1,1,3,13,63,306,1473,7085,34239,166459,813618, 3994200,19678233,97239130,481740885,2392004853, 11900655999,59312062026,296071376307, 1479998924447,7407613846698,37118966710076, 186195636158436,934889598483048,4698229684691913, 23629859054461331] |