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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 79 |
| 6 | 306 |
| 7 | 1196 |
| 8 | 4681 |
| 9 | 18308 |
| 10 | 71564 |
| 11 | 279820 |
| 12 | 1095533 |
| 13 | 4298463 |
| 14 | 16913428 |
| 15 | 66769536 |
| 16 | 264526329 |
| 17 | 1051845461 |
| 18 | 4197832133 |
| 19 | 16813161765 |
| 20 | 67571221016 |
| 21 | 272448598737 |
| 22 | 1101876945673 |
| 23 | 4469106749281 |
| 24 | 18174503562880 |
| 25 | 74093063050412 |
| 26 | 302753929958872 |
[1,1,2,6,21,79,306,1196,4681,18308,71564,279820, 1095533,4298463,16913428,66769536,264526329, 1051845461,4197832133,16813161765,67571221016, 272448598737,1101876945673,4469106749281, 18174503562880,74093063050412,302753929958872] |