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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 3 |
| 3 | 19 |
| 4 | 87 |
| 5 | 451 |
| 6 | 2223 |
| 7 | 11179 |
| 8 | 55767 |
| 9 | 279091 |
| 10 | 1394943 |
| 11 | 6975739 |
| 12 | 34876647 |
| 13 | 174387331 |
| 14 | 871928463 |
| 15 | 4359658699 |
| 16 | 21798260727 |
| 17 | 108991369171 |
| 18 | 544956714783 |
| 19 | 2724783836059 |
| 20 | 13623918656007 |
| 21 | 68119594328611 |
| 22 | 340597969545903 |
[0,1,3,19,87,451,2223,11179,55767,279091,1394943, 6975739,34876647,174387331,871928463,4359658699, 21798260727,108991369171,544956714783, 2724783836059,13623918656007,68119594328611, 340597969545903] |