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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 5 |
| 3 | 15 |
| 4 | 46 |
| 5 | 143 |
| 6 | 450 |
| 7 | 1429 |
| 8 | 4570 |
| 9 | 14698 |
| 10 | 47491 |
| 11 | 154042 |
| 12 | 501283 |
| 13 | 1635835 |
| 14 | 5351138 |
| 15 | 17541671 |
| 16 | 57610988 |
| 17 | 189521640 |
| 18 | 624389105 |
| 19 | 2059824523 |
| 20 | 6803433916 |
| 21 | 22495796651 |
| 22 | 74457478476 |
| 23 | 246667937610 |
| 24 | 817866796549 |
| 25 | 2713874203112 |
| 26 | 9011747680649 |
| 27 | 29944572743724 |
[1,2,5,15,46,143,450,1429,4570,14698,47491,154042, 501283,1635835,5351138,17541671,57610988, 189521640,624389105,2059824523,6803433916, 22495796651,74457478476,246667937610,817866796549, 2713874203112,9011747680649,29944572743724] |