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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 3 |
| 3 | 14 |
| 4 | 58 |
| 5 | 247 |
| 6 | 1045 |
| 7 | 4428 |
| 8 | 18756 |
| 9 | 79453 |
| 10 | 336567 |
| 11 | 1425722 |
| 12 | 6039454 |
| 13 | 25583539 |
| 14 | 108373609 |
| 15 | 459077976 |
| 16 | 1944685512 |
| 17 | 8237820025 |
| 18 | 34895965611 |
| 19 | 147821682470 |
| 20 | 626182695490 |
| 21 | 2652552464431 |
| 22 | 11236392553213 |
| 23 | 47598122677284 |
[0,1,3,14,58,247,1045,4428,18756,79453,336567, 1425722,6039454,25583539,108373609,459077976, 1944685512,8237820025,34895965611,147821682470, 626182695490,2652552464431,11236392553213, 47598122677284] |