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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 6 |
| 3 | 21 |
| 4 | 60 |
| 5 | 174 |
| 6 | 537 |
| 7 | 1596 |
| 8 | 4776 |
| 9 | 14358 |
| 10 | 43053 |
| 11 | 129126 |
| 12 | 387438 |
| 13 | 1162272 |
| 14 | 3486678 |
| 15 | 10460307 |
| 16 | 31380756 |
| 17 | 94141830 |
| 18 | 282426288 |
| 19 | 847278282 |
| 20 | 2541833808 |
| 21 | 7625503749 |
| 22 | 22876509444 |
| 23 | 68629525032 |
| 24 | 205888582014 |
| 25 | 617665741140 |
| 26 | 1852997213508 |
| 27 | 5558991660912 |
| 28 | 16676974967991 |
| 29 | 50030924873862 |
| 30 | 150092774683998 |
[1,3,6,21,60,174,537,1596,4776,14358,43053,129126, 387438,1162272,3486678,10460307,31380756,94141830, 282426288,847278282,2541833808,7625503749, 22876509444,68629525032,205888582014,617665741140, 1852997213508,5558991660912,16676974967991, 50030924873862,150092774683998] |