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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 9 |
| 5 | 21 |
| 6 | 50 |
| 7 | 120 |
| 8 | 290 |
| 9 | 706 |
| 10 | 1732 |
| 11 | 4280 |
| 12 | 10644 |
| 13 | 26612 |
| 14 | 66824 |
| 15 | 168384 |
| 16 | 425481 |
| 17 | 1077529 |
| 18 | 2733746 |
| 19 | 6945812 |
| 20 | 17669149 |
| 21 | 44994345 |
| 22 | 114682042 |
| 23 | 292544200 |
| 24 | 746831570 |
| 25 | 1907983346 |
| 26 | 4877966628 |
| 27 | 12479883736 |
| 28 | 31951158024 |
| 29 | 81858610968 |
| 30 | 209865391600 |
| 31 | 538408691456 |
[1,1,2,4,9,21,50,120,290,706,1732,4280,10644, 26612,66824,168384,425481,1077529,2733746,6945812, 17669149,44994345,114682042,292544200,746831570, 1907983346,4877966628,12479883736,31951158024, 81858610968,209865391600,538408691456] |