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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 72 |
| 6 | 229 |
| 7 | 683 |
| 8 | 1954 |
| 9 | 5452 |
| 10 | 14974 |
| 11 | 40671 |
| 12 | 109509 |
| 13 | 292743 |
| 14 | 777810 |
| 15 | 2055833 |
| 16 | 5409187 |
| 17 | 14175902 |
| 18 | 37020669 |
| 19 | 96378274 |
| 20 | 250204801 |
| 21 | 647907945 |
| 22 | 1673920904 |
| 23 | 4315683002 |
| 24 | 11105412898 |
| 25 | 28527156939 |
| 26 | 73161209063 |
| 27 | 187350573875 |
[1,2,6,21,72,229,683,1954,5452,14974,40671,109509, 292743,777810,2055833,5409187,14175902,37020669, 96378274,250204801,647907945,1673920904, 4315683002,11105412898,28527156939,73161209063, 187350573875] |