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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 18 |
| 2 | 123 |
| 3 | 523 |
| 4 | 1673 |
| 5 | 4424 |
| 6 | 10206 |
| 7 | 21246 |
| 8 | 40821 |
| 9 | 73546 |
| 10 | 125697 |
| 11 | 205569 |
| 12 | 323869 |
| 13 | 494144 |
| 14 | 733244 |
| 15 | 1061820 |
| 16 | 1504857 |
| 17 | 2092242 |
| 18 | 2859367 |
| 19 | 3847767 |
| 20 | 5105793 |
| 21 | 6689320 |
| 22 | 8662490 |
| 23 | 11098490 |
| 24 | 14080365 |
| 25 | 17701866 |
| 26 | 22068333 |
| 27 | 27297613 |
| 28 | 33521013 |
| 29 | 40884288 |
[1,18,123,523,1673,4424,10206,21246,40821,73546, 125697,205569,323869,494144,733244,1061820, 1504857,2092242,2859367,3847767,5105793,6689320, 8662490,11098490,14080365,17701866,22068333, 27297613,33521013,40884288] |