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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 18 |
| 3 | 78 |
| 4 | 281 |
| 5 | 1072 |
| 6 | 4033 |
| 7 | 15255 |
| 8 | 57963 |
| 9 | 220068 |
| 10 | 835820 |
| 11 | 3172817 |
| 12 | 12044346 |
| 13 | 45722019 |
| 14 | 173574485 |
| 15 | 658947323 |
| 16 | 2501581220 |
| 17 | 9496787730 |
| 18 | 36052730049 |
| 19 | 136867284190 |
| 20 | 519590670019 |
| 21 | 1972527813429 |
| 22 | 7488329193659 |
| 23 | 28428025632710 |
[1,18,78,281,1072,4033,15255,57963,220068,835820, 3172817,12044346,45722019,173574485,658947323, 2501581220,9496787730,36052730049,136867284190, 519590670019,1972527813429,7488329193659, 28428025632710] |