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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 42 |
| 5 | 153 |
| 6 | 593 |
| 7 | 2333 |
| 8 | 9522 |
| 9 | 39283 |
| 10 | 165815 |
| 11 | 706828 |
| 12 | 3058009 |
| 13 | 13331249 |
| 14 | 58754207 |
| 15 | 260519211 |
| 16 | 1164703413 |
| 17 | 5233155799 |
| 18 | 23664405546 |
| 19 | 107456289612 |
| 20 | 490466225257 |
| 21 | 2246496796421 |
| 22 | 10333356366661 |
| 23 | 47673400810091 |
| 24 | 220721796088564 |
| 25 | 1024559018474286 |
| 26 | 4770112516366437 |
| 27 | 22258699966303098 |
[1,1,4,12,42,153,593,2333,9522,39283,165815, 706828,3058009,13331249,58754207,260519211, 1164703413,5233155799,23664405546,107456289612, 490466225257,2246496796421,10333356366661, 47673400810091,220721796088564,1024559018474286, 4770112516366437,22258699966303098] |