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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 13 |
| 4 | 55 |
| 5 | 206 |
| 6 | 929 |
| 7 | 3854 |
| 8 | 17797 |
| 9 | 77497 |
| 10 | 364043 |
| 11 | 1636237 |
| 12 | 7772563 |
| 13 | 35679961 |
| 14 | 170863707 |
| 15 | 796256786 |
| 16 | 3836089543 |
| 17 | 18077155221 |
| 18 | 87495240136 |
| 19 | 415839255346 |
| 20 | 2020128721725 |
| 21 | 9665396470341 |
| 22 | 47094220547527 |
| 23 | 226531339610481 |
| 24 | 1106476770045798 |
| 25 | 5345538685045776 |
| 26 | 26163552380725908 |
| 27 | 126854484533770709 |
[1,1,4,13,55,206,929,3854,17797,77497,364043, 1636237,7772563,35679961,170863707,796256786, 3836089543,18077155221,87495240136,415839255346, 2020128721725,9665396470341,47094220547527, 226531339610481,1106476770045798,5345538685045776, 26163552380725908,126854484533770709] |