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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 15 |
| 3 | 75 |
| 4 | 400 |
| 5 | 2169 |
| 6 | 11989 |
| 7 | 66985 |
| 8 | 377718 |
| 9 | 2144290 |
| 10 | 12240943 |
| 11 | 70193305 |
| 12 | 404029950 |
| 13 | 2332989921 |
| 14 | 13508237399 |
| 15 | 78399357623 |
| 16 | 455959701700 |
| 17 | 2656652705422 |
| 18 | 15504203678738 |
| 19 | 90614205677898 |
| 20 | 530288460288008 |
| 21 | 3107012752773125 |
| 22 | 18223934202102463 |
| 23 | 106996319699099591 |
[1,3,15,75,400,2169,11989,66985,377718,2144290, 12240943,70193305,404029950,2332989921, 13508237399,78399357623,455959701700, 2656652705422,15504203678738,90614205677898, 530288460288008,3107012752773125, 18223934202102463,106996319699099591] |