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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 5 |
| 5 | 14 |
| 6 | 43 |
| 7 | 140 |
| 8 | 478 |
| 9 | 1695 |
| 10 | 6205 |
| 11 | 23356 |
| 12 | 90135 |
| 13 | 355960 |
| 14 | 1436755 |
| 15 | 5922799 |
| 16 | 24929035 |
| 17 | 107136291 |
| 18 | 470281976 |
| 19 | 2109608447 |
| 20 | 9677546281 |
| 21 | 45434467501 |
| 22 | 218478232454 |
| 23 | 1076855324959 |
| 24 | 5443845581547 |
| 25 | 28239060235110 |
| 26 | 150346623540441 |
| 27 | 821555490484095 |
[1,1,1,2,5,14,43,140,478,1695,6205,23356,90135, 355960,1436755,5922799,24929035,107136291, 470281976,2109608447,9677546281,45434467501, 218478232454,1076855324959,5443845581547, 28239060235110,150346623540441,821555490484095] |