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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 2 |
| 3 | 6 |
| 4 | 22 |
| 5 | 50 |
| 6 | 274 |
| 7 | 598 |
| 8 | 4486 |
| 9 | 9570 |
| 10 | 90914 |
| 11 | 191398 |
| 12 | 2201078 |
| 13 | 4593554 |
| 14 | 62012978 |
| 15 | 128619510 |
| 16 | 1993602406 |
| 17 | 4115824322 |
| 18 | 72026925634 |
| 19 | 148169675590 |
| 20 | 2889308674006 |
[1,2,2,6,22,50,274,598,4486,9570,90914,191398, 2201078,4593554,62012978,128619510,1993602406, 4115824322,72026925634,148169675590,2889308674006] |