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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 15 |
| 3 | 82 |
| 4 | 504 |
| 5 | 3198 |
| 6 | 21592 |
| 7 | 147570 |
| 8 | 1045221 |
| 9 | 7464052 |
| 10 | 54549804 |
| 11 | 400487997 |
| 12 | 2990765270 |
| 13 | 22396990002 |
| 14 | 169881957174 |
| 15 | 1291189065086 |
| 16 | 9910770901971 |
| 17 | 76178174174205 |
| 18 | 590312326353680 |
| 19 | 4578346159792815 |
| 20 | 35745960436892046 |
| 21 | 279290158338688617 |
[1,3,15,82,504,3198,21592,147570,1045221,7464052, 54549804,400487997,2990765270,22396990002, 169881957174,1291189065086,9910770901971, 76178174174205,590312326353680,4578346159792815, 35745960436892046,279290158338688617] |