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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 10 |
| 4 | 42 |
| 5 | 136 |
| 6 | 598 |
| 7 | 2162 |
| 8 | 9815 |
| 9 | 37636 |
| 10 | 174615 |
| 11 | 694695 |
| 12 | 3271551 |
| 13 | 13352629 |
| 14 | 63547908 |
| 15 | 264327829 |
| 16 | 1267696988 |
| 17 | 5350969987 |
| 18 | 25811875559 |
| 19 | 110238766866 |
| 20 | 534157611947 |
| 21 | 2303345758002 |
| 22 | 11200561768291 |
| 23 | 48687212201572 |
| 24 | 237436053622265 |
| 25 | 1039149699997593 |
| 26 | 5079720276433999 |
| 27 | 22362113435873612 |
[1,1,4,10,42,136,598,2162,9815,37636,174615, 694695,3271551,13352629,63547908,264327829, 1267696988,5350969987,25811875559,110238766866, 534157611947,2303345758002,11200561768291, 48687212201572,237436053622265,1039149699997593, 5079720276433999,22362113435873612] |