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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 39 |
| 5 | 142 |
| 6 | 545 |
| 7 | 2106 |
| 8 | 8382 |
| 9 | 34215 |
| 10 | 142643 |
| 11 | 600014 |
| 12 | 2557631 |
| 13 | 11028505 |
| 14 | 48020121 |
| 15 | 210769413 |
| 16 | 931363949 |
| 17 | 4143384678 |
| 18 | 18544445680 |
| 19 | 83436432216 |
| 20 | 377186393627 |
| 21 | 1712438625809 |
| 22 | 7806272131532 |
| 23 | 35718243832372 |
| 24 | 163985930358341 |
| 25 | 755228559001683 |
| 26 | 3488271916047151 |
| 27 | 16155889488916942 |
[1,1,4,12,39,142,545,2106,8382,34215,142643, 600014,2557631,11028505,48020121,210769413, 931363949,4143384678,18544445680,83436432216, 377186393627,1712438625809,7806272131532, 35718243832372,163985930358341,755228559001683, 3488271916047151,16155889488916942] |