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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 18 |
| 3 | 94 |
| 4 | 424 |
| 5 | 1854 |
| 6 | 7628 |
| 7 | 30874 |
| 8 | 123312 |
| 9 | 488256 |
| 10 | 1920790 |
| 11 | 7513678 |
| 12 | 29249892 |
| 13 | 113386708 |
| 14 | 437908264 |
| 15 | 1685639238 |
| 16 | 6469357240 |
| 17 | 24762845248 |
| 18 | 94557090250 |
| 19 | 360277506538 |
| 20 | 1369975634630 |
| 21 | 5199885300498 |
| 22 | 19703519987286 |
| 23 | 74545164231536 |
[2,18,94,424,1854,7628,30874,123312,488256, 1920790,7513678,29249892,113386708,437908264, 1685639238,6469357240,24762845248,94557090250, 360277506538,1369975634630,5199885300498, 19703519987286,74545164231536] |