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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 4 |
| 4 | 11 |
| 5 | 53 |
| 6 | 146 |
| 7 | 366 |
| 8 | 1563 |
| 9 | 5837 |
| 10 | 16720 |
| 11 | 59917 |
| 12 | 246090 |
| 13 | 828157 |
| 14 | 2773984 |
| 15 | 11056545 |
| 16 | 41539923 |
| 17 | 142602611 |
| 18 | 536781500 |
| 19 | 2103092222 |
| 20 | 7632057148 |
| 21 | 27948758125 |
| 22 | 108960963441 |
| 23 | 413531196001 |
| 24 | 1523673835870 |
| 25 | 5833675306068 |
| 26 | 22596747340839 |
| 27 | 85028853983908 |
| 28 | 322415760345476 |
[1,1,3,4,11,53,146,366,1563,5837,16720,59917, 246090,828157,2773984,11056545,41539923,142602611, 536781500,2103092222,7632057148,27948758125, 108960963441,413531196001,1523673835870, 5833675306068,22596747340839,85028853983908, 322415760345476] |