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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 74 |
| 6 | 249 |
| 7 | 797 |
| 8 | 2451 |
| 9 | 7318 |
| 10 | 21380 |
| 11 | 61449 |
| 12 | 174378 |
| 13 | 489827 |
| 14 | 1364499 |
| 15 | 3774779 |
| 16 | 10381722 |
| 17 | 28410568 |
| 18 | 77414615 |
| 19 | 210156558 |
| 20 | 568645563 |
| 21 | 1534219643 |
| 22 | 4128788739 |
| 23 | 11085822020 |
| 24 | 29704820778 |
| 25 | 79449163033 |
| 26 | 212145068252 |
| 27 | 565621458225 |
| 28 | 1506010540935 |
| 29 | 4004905219913 |
[1,1,2,6,21,74,249,797,2451,7318,21380,61449, 174378,489827,1364499,3774779,10381722,28410568, 77414615,210156558,568645563,1534219643, 4128788739,11085822020,29704820778,79449163033, 212145068252,565621458225,1506010540935, 4004905219913] |