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| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 3 |
| 4 | 18 |
| 5 | 55 |
| 6 | 264 |
| 7 | 847 |
| 8 | 3744 |
| 9 | 12465 |
| 10 | 52868 |
| 11 | 180895 |
| 12 | 749220 |
| 13 | 2617173 |
| 14 | 10680656 |
| 15 | 37915317 |
| 16 | 153240864 |
| 17 | 551019963 |
| 18 | 2212417314 |
| 19 | 8038946075 |
| 20 | 32129224712 |
| 21 | 117758845827 |
| 22 | 469105048654 |
| 23 | 1731917060158 |
| 24 | 6882935960496 |
| 25 | 25569740611270 |
| 26 | 101442831429264 |
| 27 | 378875492015643 |
[1,3,18,55,264,847,3744,12465,52868,180895,749220, 2617173,10680656,37915317,153240864,551019963, 2212417314,8038946075,32129224712,117758845827, 469105048654,1731917060158,6882935960496, 25569740611270,101442831429264,378875492015643] |