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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 19 |
| 4 | 70 |
| 5 | 272 |
| 6 | 1102 |
| 7 | 4603 |
| 8 | 19689 |
| 9 | 85905 |
| 10 | 380419 |
| 11 | 1706952 |
| 12 | 7740063 |
| 13 | 35416953 |
| 14 | 163311951 |
| 15 | 758082996 |
| 16 | 3539424469 |
| 17 | 16609301242 |
| 18 | 78292331761 |
| 19 | 370522059204 |
| 20 | 1759756397921 |
| 21 | 8384450205934 |
| 22 | 40063002574731 |
| 23 | 191928810878505 |
| 24 | 921638909638874 |
| 25 | 4435212118443270 |
| 26 | 21385562185737670 |
| 27 | 103301985771383536 |
[1,2,6,19,70,272,1102,4603,19689,85905,380419, 1706952,7740063,35416953,163311951,758082996, 3539424469,16609301242,78292331761,370522059204, 1759756397921,8384450205934,40063002574731, 191928810878505,921638909638874,4435212118443270, 21385562185737670,103301985771383536] |