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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 22 |
| 5 | 86 |
| 6 | 337 |
| 7 | 1299 |
| 8 | 4910 |
| 9 | 18228 |
| 10 | 66640 |
| 11 | 240550 |
| 12 | 859295 |
| 13 | 3043525 |
| 14 | 10705182 |
| 15 | 37441618 |
| 16 | 130351650 |
| 17 | 452119862 |
| 18 | 1563402141 |
| 19 | 5392828631 |
| 20 | 18564966510 |
| 21 | 63807048144 |
| 22 | 219015409556 |
| 23 | 750968486726 |
| 24 | 2572756726459 |
| 25 | 8808011192329 |
| 26 | 30138217809470 |
| 27 | 103077794599470 |
[1,2,6,22,86,337,1299,4910,18228,66640,240550, 859295,3043525,10705182,37441618,130351650, 452119862,1563402141,5392828631,18564966510, 63807048144,219015409556,750968486726, 2572756726459,8808011192329,30138217809470, 103077794599470] |