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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 20 |
| 4 | 70 |
| 5 | 253 |
| 6 | 938 |
| 7 | 3546 |
| 8 | 13617 |
| 9 | 52967 |
| 10 | 208255 |
| 11 | 826315 |
| 12 | 3304456 |
| 13 | 13304924 |
| 14 | 53891402 |
| 15 | 219442686 |
| 16 | 897772983 |
| 17 | 3688451380 |
| 18 | 15211545938 |
| 19 | 62950542636 |
| 20 | 261329456566 |
| 21 | 1087985751336 |
| 22 | 4541524025769 |
| 23 | 19003488710465 |
| 24 | 79696345430789 |
[1,2,6,20,70,253,938,3546,13617,52967,208255, 826315,3304456,13304924,53891402,219442686, 897772983,3688451380,15211545938,62950542636, 261329456566,1087985751336,4541524025769, 19003488710465,79696345430789] |